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nlohmann::basic_json Class Reference

a class to store JSON values More...

#include <json.hpp>

+ Collaboration diagram for nlohmann::basic_json:

Public Types

using cbor_tag_handler_t = detail::cbor_tag_handler_t
 how to treat CBOR tags More...
 
using error_handler_t = detail::error_handler_t
 how to treat decoding errors More...
 
using initializer_list_t = std::initializer_list< detail::json_ref< basic_json > >
 helper type for initializer lists of basic_json values More...
 
using input_format_t = detail::input_format_t
 
using json_pointer = ::nlohmann::json_pointer< basic_json >
 JSON Pointer, see nlohmann::json_pointer. More...
 
using json_sax_t = json_sax< basic_json >
 SAX interface type, see nlohmann::json_sax. More...
 
template<typename T , typename SFINAE >
using json_serializer = JSONSerializer< T, SFINAE >
 
using parse_event_t = detail::parse_event_t
 parser event types More...
 
using parser_callback_t = detail::parser_callback_t< basic_json >
 per-element parser callback type More...
 
using value_t = detail::value_t
 

Public Member Functions

const JSON_HEDLEY_RETURNS_NON_NULL char * type_name () const noexcept
 return the type as string More...
 

Static Public Member Functions

static allocator_type get_allocator ()
 returns the allocator associated with the container More...
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json meta ()
 returns version information on the library More...
 

Data Fields

JSON_PRIVATE_UNLESS_TESTED __pad3__: value_t m_type = value_t::null
 
json_value m_value = {}
 the value of the current element More...
 

Private Types

using basic_json_t = NLOHMANN_BASIC_JSON_TPL
 workaround type for MSVC More...
 
template<typename InputType >
using binary_reader = ::nlohmann::detail::binary_reader< basic_json, InputType >
 
template<typename CharType >
using binary_writer = ::nlohmann::detail::binary_writer< basic_json, CharType >
 
template<typename BasicJsonType >
using internal_iterator = ::nlohmann::detail::internal_iterator< BasicJsonType >
 
template<typename BasicJsonType >
using iter_impl = ::nlohmann::detail::iter_impl< BasicJsonType >
 
template<typename Iterator >
using iteration_proxy = ::nlohmann::detail::iteration_proxy< Iterator >
 
template<typename Base >
using json_reverse_iterator = ::nlohmann::detail::json_reverse_iterator< Base >
 
template<typename CharType >
using output_adapter_t = ::nlohmann::detail::output_adapter_t< CharType >
 
using primitive_iterator_t = ::nlohmann::detail::primitive_iterator_t
 

Private Member Functions

void assert_invariant (bool check_parents=true) const noexcept
 checks the class invariants More...
 
void destroy (value_t t)
 
boolean_t get_impl (boolean_t *) const
 get a boolean (explicit) More...
 
array_tget_impl_ptr (array_t *) noexcept
 get a pointer to the value (array) More...
 
binary_tget_impl_ptr (binary_t *) noexcept
 get a pointer to the value (binary) More...
 
boolean_tget_impl_ptr (boolean_t *) noexcept
 get a pointer to the value (boolean) More...
 
constexpr const array_tget_impl_ptr (const array_t *) const noexcept
 get a pointer to the value (array) More...
 
constexpr const binary_tget_impl_ptr (const binary_t *) const noexcept
 get a pointer to the value (binary) More...
 
constexpr const boolean_tget_impl_ptr (const boolean_t *) const noexcept
 get a pointer to the value (boolean) More...
 
constexpr const number_float_tget_impl_ptr (const number_float_t *) const noexcept
 get a pointer to the value (floating-point number) More...
 
constexpr const number_integer_tget_impl_ptr (const number_integer_t *) const noexcept
 get a pointer to the value (integer number) More...
 
constexpr const number_unsigned_tget_impl_ptr (const number_unsigned_t *) const noexcept
 get a pointer to the value (unsigned number) More...
 
constexpr const object_tget_impl_ptr (const object_t *) const noexcept
 get a pointer to the value (object) More...
 
constexpr const string_tget_impl_ptr (const string_t *) const noexcept
 get a pointer to the value (string) More...
 
number_float_tget_impl_ptr (number_float_t *) noexcept
 get a pointer to the value (floating-point number) More...
 
number_integer_tget_impl_ptr (number_integer_t *) noexcept
 get a pointer to the value (integer number) More...
 
number_unsigned_tget_impl_ptr (number_unsigned_t *) noexcept
 get a pointer to the value (unsigned number) More...
 
object_tget_impl_ptr (object_t *) noexcept
 get a pointer to the value (object) More...
 
string_tget_impl_ptr (string_t *) noexcept
 get a pointer to the value (string) More...
 
 json_value ()=default
 default constructor (for null values) More...
 
 json_value (array_t &&value)
 constructor for rvalue arrays More...
 
 json_value (binary_t &&value)
 constructor for rvalue binary arrays (internal type) More...
 
 json_value (boolean_t v) noexcept
 constructor for booleans More...
 
 json_value (const array_t &value)
 constructor for arrays More...
 
 json_value (const binary_t &value)
 constructor for binary arrays (internal type) More...
 
 json_value (const object_t &value)
 constructor for objects More...
 
 json_value (const string_t &value)
 constructor for strings More...
 
 json_value (const typename binary_t::container_type &value)
 constructor for binary arrays More...
 
 json_value (number_float_t v) noexcept
 constructor for numbers (floating-point) More...
 
 json_value (number_integer_t v) noexcept
 constructor for numbers (integer) More...
 
 json_value (number_unsigned_t v) noexcept
 constructor for numbers (unsigned) More...
 
 json_value (object_t &&value)
 constructor for rvalue objects More...
 
 json_value (string_t &&value)
 constructor for rvalue strings More...
 
 json_value (typename binary_t::container_type &&value)
 constructor for rvalue binary arrays More...
 
 json_value (value_t t)
 constructor for empty values of a given type More...
 
template<typename InputAdapterType >
static ::nlohmann::detail::parser< basic_json, InputAdapterType > parser (InputAdapterType adapter, detail::parser_callback_t< basic_json >cb=nullptr, const bool allow_exceptions=true, const bool ignore_comments=false)
 
reference set_parent (reference j, std::size_t old_capacity=std::size_t(-1))
 
void set_parents ()
 
iterator set_parents (iterator it, typename iterator::difference_type count)
 

Static Private Member Functions

template<typename T , typename... Args>
static JSON_HEDLEY_RETURNS_NON_NULL T * create (Args &&... args)
 helper for exception-safe object creation More...
 
template<typename ReferenceType , typename ThisType >
static ReferenceType get_ref_impl (ThisType &obj)
 helper function to implement get_ref() More...
 

Private Attributes

JSON_PRIVATE_UNLESS_TESTED __pad0__: using lexer = ::nlohmann::detail::lexer_base<basic_json>
 
JSON_PRIVATE_UNLESS_TESTED __pad1__: using serializer = ::nlohmann::detail::serializer<basic_json>
 
JSON_PRIVATE_UNLESS_TESTED __pad2__: union json_value { object_t* object
 
array_tarray
 array (stored with pointer to save storage) More...
 
binary_tbinary
 binary (stored with pointer to save storage) More...
 
boolean_t boolean
 boolean More...
 
number_float_t number_float
 number (floating-point) More...
 
number_integer_t number_integer
 number (integer) More...
 
number_unsigned_t number_unsigned
 number (unsigned integer) More...
 
string_tstring
 string (stored with pointer to save storage) More...
 

Friends

template<typename BasicJsonType , typename InputType , typename SAX >
class ::nlohmann::detail::binary_reader
 
template<typename BasicJsonType , typename CharType >
class ::nlohmann::detail::binary_writer
 
class ::nlohmann::detail::exception
 
template<typename BasicJsonType >
class ::nlohmann::detail::iter_impl
 
template<typename BasicJsonType >
class ::nlohmann::detail::json_sax_dom_callback_parser
 
template<typename BasicJsonType >
class ::nlohmann::detail::json_sax_dom_parser
 
template<typename BasicJsonType , typename InputType >
class ::nlohmann::detail::parser
 
template<detail::value_t >
struct detail::external_constructor
 

exceptions

Classes to implement user-defined exceptions.

using exception = detail::exception
 general exception of the basic_json class More...
 
using parse_error = detail::parse_error
 exception indicating a parse error More...
 
using invalid_iterator = detail::invalid_iterator
 exception indicating errors with iterators More...
 
using type_error = detail::type_error
 exception indicating executing a member function with a wrong type More...
 
using out_of_range = detail::out_of_range
 exception indicating access out of the defined range More...
 
using other_error = detail::other_error
 exception indicating other library errors More...
 

container types

The canonic container types to use basic_json like any other STL container.

using value_type = basic_json
 the type of elements in a basic_json container More...
 
using reference = value_type &
 the type of an element reference More...
 
using const_reference = const value_type &
 the type of an element const reference More...
 
using difference_type = std::ptrdiff_t
 a type to represent differences between iterators More...
 
using size_type = std::size_t
 a type to represent container sizes More...
 
using allocator_type = AllocatorType< basic_json >
 the allocator type More...
 
using pointer = typename std::allocator_traits< allocator_type >::pointer
 the type of an element pointer More...
 
using const_pointer = typename std::allocator_traits< allocator_type >::const_pointer
 the type of an element const pointer More...
 
using iterator = iter_impl< basic_json >
 an iterator for a basic_json container More...
 
using const_iterator = iter_impl< const basic_json >
 a const iterator for a basic_json container More...
 
using reverse_iterator = json_reverse_iterator< typename basic_json::iterator >
 a reverse iterator for a basic_json container More...
 
using const_reverse_iterator = json_reverse_iterator< typename basic_json::const_iterator >
 a const reverse iterator for a basic_json container More...
 

JSON value data types

The data types to store a JSON value. These types are derived from the template arguments passed to class basic_json.

using object_comparator_t = std::less< StringType >
 
using object_t = ObjectType< StringType, basic_json, object_comparator_t, AllocatorType< std::pair< const StringType, basic_json > >>
 a type for an object More...
 
using array_t = ArrayType< basic_json, AllocatorType< basic_json > >
 a type for an array More...
 
using string_t = StringType
 a type for a string More...
 
using boolean_t = BooleanType
 a type for a boolean More...
 
using number_integer_t = NumberIntegerType
 a type for a number (integer) More...
 
using number_unsigned_t = NumberUnsignedType
 a type for a number (unsigned) More...
 
using number_float_t = NumberFloatType
 a type for a number (floating-point) More...
 
using binary_t = nlohmann::byte_container_with_subtype< BinaryType >
 a type for a packed binary type More...
 

constructors and destructors

Constructors of class basic_json, copy/move constructor, copy assignment, static functions creating objects, and the destructor.

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json binary (const typename binary_t::container_type &init)
 explicitly create a binary array (without subtype) More...
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json binary (const typename binary_t::container_type &init, typename binary_t::subtype_type subtype)
 explicitly create a binary array (with subtype) More...
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json binary (typename binary_t::container_type &&init)
 explicitly create a binary array (without subtype) More...
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json binary (typename binary_t::container_type &&init, typename binary_t::subtype_type subtype)
 explicitly create a binary array (with subtype) More...
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json array (initializer_list_t init={})
 explicitly create an array from an initializer list More...
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json object (initializer_list_t init={})
 explicitly create an object from an initializer list More...
 
 basic_json (const value_t v)
 create an empty value with a given type More...
 
 basic_json (std::nullptr_t=nullptr) noexcept
 create a null object More...
 
template<typename CompatibleType , typename U = detail::uncvref_t<CompatibleType>, detail::enable_if_t< !detail::is_basic_json< U >::value &&detail::is_compatible_type< basic_json_t, U >::value, int > = 0>
 basic_json (CompatibleType &&val) noexcept(noexcept(//NOLINT(bugprone-forwarding-reference-overload, bugprone-exception-escape) JSONSerializer< U >::to_json(std::declval< basic_json_t & >(), std::forward< CompatibleType >(val))))
 create a JSON value More...
 
template<typename BasicJsonType , detail::enable_if_t< detail::is_basic_json< BasicJsonType >::value &&!std::is_same< basic_json, BasicJsonType >::value, int > = 0>
 basic_json (const BasicJsonType &val)
 create a JSON value from an existing one More...
 
 basic_json (initializer_list_t init, bool type_deduction=true, value_t manual_type=value_t::array)
 create a container (array or object) from an initializer list More...
 
 basic_json (size_type cnt, const basic_json &val)
 construct an array with count copies of given value More...
 
template<class InputIT , typename std::enable_if< std::is_same< InputIT, typename basic_json_t::iterator >::value||std::is_same< InputIT, typename basic_json_t::const_iterator >::value, int >::type = 0>
 basic_json (InputIT first, InputIT last)
 construct a JSON container given an iterator range More...
 
template<typename JsonRef , detail::enable_if_t< detail::conjunction< detail::is_json_ref< JsonRef >, std::is_same< typename JsonRef::value_type, basic_json >>::value, int > = 0>
 basic_json (const JsonRef &ref)
 
 basic_json (const basic_json &other)
 copy constructor More...
 
 basic_json (basic_json &&other) noexcept
 move constructor More...
 
basic_jsonoperator= (basic_json other) noexcept(std::is_nothrow_move_constructible< value_t >::value &&std::is_nothrow_move_assignable< value_t >::value &&std::is_nothrow_move_constructible< json_value >::value &&std::is_nothrow_move_assignable< json_value >::value)
 copy assignment More...
 
 ~basic_json () noexcept
 destructor More...
 

object inspection

Functions to inspect the type of a JSON value.

string_t dump (const int indent=-1, const char indent_char=' ', const bool ensure_ascii=false, const error_handler_t error_handler=error_handler_t::strict) const
 serialization More...
 
constexpr value_t type () const noexcept
 return the type of the JSON value (explicit) More...
 
constexpr bool is_primitive () const noexcept
 return whether type is primitive More...
 
constexpr bool is_structured () const noexcept
 return whether type is structured More...
 
constexpr bool is_null () const noexcept
 return whether value is null More...
 
constexpr bool is_boolean () const noexcept
 return whether value is a boolean More...
 
constexpr bool is_number () const noexcept
 return whether value is a number More...
 
constexpr bool is_number_integer () const noexcept
 return whether value is an integer number More...
 
constexpr bool is_number_unsigned () const noexcept
 return whether value is an unsigned integer number More...
 
constexpr bool is_number_float () const noexcept
 return whether value is a floating-point number More...
 
constexpr bool is_object () const noexcept
 return whether value is an object More...
 
constexpr bool is_array () const noexcept
 return whether value is an array More...
 
constexpr bool is_string () const noexcept
 return whether value is a string More...
 
constexpr bool is_binary () const noexcept
 return whether value is a binary array More...
 
constexpr bool is_discarded () const noexcept
 return whether value is discarded More...
 
constexpr operator value_t () const noexcept
 return the type of the JSON value (implicit) More...
 

value access

Direct access to the stored value of a JSON value.

template<typename ValueType , detail::enable_if_t< detail::is_default_constructible< ValueType >::value &&detail::has_from_json< basic_json_t, ValueType >::value, int > = 0>
ValueType get_impl (detail::priority_tag< 0 >) const noexcept(noexcept(JSONSerializer< ValueType >::from_json(std::declval< const basic_json_t & >(), std::declval< ValueType & >())))
 get a value (explicit) More...
 
template<typename ValueType , detail::enable_if_t< detail::has_non_default_from_json< basic_json_t, ValueType >::value, int > = 0>
ValueType get_impl (detail::priority_tag< 1 >) const noexcept(noexcept(JSONSerializer< ValueType >::from_json(std::declval< const basic_json_t & >())))
 get a value (explicit); special case More...
 
template<typename BasicJsonType , detail::enable_if_t< detail::is_basic_json< BasicJsonType >::value, int > = 0>
BasicJsonType get_impl (detail::priority_tag< 2 >) const
 get special-case overload More...
 
template<typename BasicJsonType , detail::enable_if_t< std::is_same< BasicJsonType, basic_json_t >::value, int > = 0>
basic_json get_impl (detail::priority_tag< 3 >) const
 get special-case overload More...
 
template<typename PointerType , detail::enable_if_t< std::is_pointer< PointerType >::value, int > = 0>
constexpr auto get_impl (detail::priority_tag< 4 >) const noexcept -> decltype(std::declval< const basic_json_t & >().template get_ptr< PointerType >())
 get a pointer value (explicit) More...
 
template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::value, int >::type = 0>
auto get_ptr () noexcept -> decltype(std::declval< basic_json_t & >().get_impl_ptr(std::declval< PointerType >()))
 get a pointer value (implicit) More...
 
template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::value &&std::is_const< typename std::remove_pointer< PointerType >::type >::value, int >::type = 0>
constexpr auto get_ptr () const noexcept -> decltype(std::declval< const basic_json_t & >().get_impl_ptr(std::declval< PointerType >()))
 get a pointer value (implicit) More...
 
template<typename ValueTypeCV , typename ValueType = detail::uncvref_t<ValueTypeCV>>
auto get () const noexcept(noexcept(std::declval< const basic_json_t & >().template get_impl< ValueType >(detail::priority_tag< 4 > {}))) -> decltype(std::declval< const basic_json_t & >().template get_impl< ValueType >(detail::priority_tag< 4 >
 get a (pointer) value (explicit) More...
 
return get_impl (detail::priority_tag< 4 > {})
 
template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::value, int >::type = 0>
auto get () noexcept -> decltype(std::declval< basic_json_t & >().template get_ptr< PointerType >())
 get a pointer value (explicit) More...
 
template<typename ValueType , detail::enable_if_t< !detail::is_basic_json< ValueType >::value &&detail::has_from_json< basic_json_t, ValueType >::value, int > = 0>
ValueType & get_to (ValueType &v) const noexcept(noexcept(JSONSerializer< ValueType >::from_json(std::declval< const basic_json_t & >(), v)))
 get a value (explicit) More...
 
template<typename ValueType , detail::enable_if_t< detail::is_basic_json< ValueType >::value, int > = 0>
ValueType & get_to (ValueType &v) const
 
template<typename T , std::size_t N, typename Array = T (&)[N], detail::enable_if_t< detail::has_from_json< basic_json_t, Array >::value, int > = 0>
Array get_to (T(&v)[N]) const noexcept(noexcept(JSONSerializer< Array >::from_json(std::declval< const basic_json_t & >(), v)))
 
template<typename ReferenceType , typename std::enable_if< std::is_reference< ReferenceType >::value, int >::type = 0>
ReferenceType get_ref ()
 get a reference value (implicit) More...
 
template<typename ReferenceType , typename std::enable_if< std::is_reference< ReferenceType >::value &&std::is_const< typename std::remove_reference< ReferenceType >::type >::value, int >::type = 0>
ReferenceType get_ref () const
 get a reference value (implicit) More...
 
template<typename ValueType , typename std::enable_if< detail::conjunction< detail::negation< std::is_pointer< ValueType >>, detail::negation< std::is_same< ValueType, detail::json_ref< basic_json >>>, detail::negation< std::is_same< ValueType, typename string_t::value_type >>, detail::negation< detail::is_basic_json< ValueType >>, detail::negation< std::is_same< ValueType, std::initializer_list< typename string_t::value_type >>>, detail::is_detected_lazy< detail::get_template_function, const basic_json_t &, ValueType > >::value, int >::type = 0>
JSON_EXPLICIT operator ValueType () const
 get a value (implicit) More...
 
binary_tget_binary ()
 
const binary_tget_binary () const
 

element access

Access to the JSON value.

reference at (size_type idx)
 access specified array element with bounds checking More...
 
const_reference at (size_type idx) const
 access specified array element with bounds checking More...
 
reference at (const typename object_t::key_type &key)
 access specified object element with bounds checking More...
 
const_reference at (const typename object_t::key_type &key) const
 access specified object element with bounds checking More...
 
reference operator[] (size_type idx)
 access specified array element More...
 
const_reference operator[] (size_type idx) const
 access specified array element More...
 
reference operator[] (const typename object_t::key_type &key)
 access specified object element More...
 
const_reference operator[] (const typename object_t::key_type &key) const
 read-only access specified object element More...
 
template<typename T >
reference operator[] (T *key)
 access specified object element More...
 
template<typename T >
const_reference operator[] (T *key) const
 read-only access specified object element More...
 
template<class ValueType , typename std::enable_if< detail::is_getable< basic_json_t, ValueType >::value &&!std::is_same< value_t, ValueType >::value, int >::type = 0>
ValueType value (const typename object_t::key_type &key, const ValueType &default_value) const
 access specified object element with default value More...
 
string_t value (const typename object_t::key_type &key, const char *default_value) const
 overload for a default value of type const char* More...
 
template<class ValueType , typename std::enable_if< detail::is_getable< basic_json_t, ValueType >::value, int >::type = 0>
ValueType value (const json_pointer &ptr, const ValueType &default_value) const
 access specified object element via JSON Pointer with default value More...
 
string_t value (const json_pointer &ptr, const char *default_value) const
 overload for a default value of type const char* More...
 
reference front ()
 access the first element More...
 
const_reference front () const
 access the first element More...
 
reference back ()
 access the last element More...
 
const_reference back () const
 access the last element More...
 
template<class IteratorType , typename std::enable_if< std::is_same< IteratorType, typename basic_json_t::iterator >::value||std::is_same< IteratorType, typename basic_json_t::const_iterator >::value, int >::type = 0>
IteratorType erase (IteratorType pos)
 remove element given an iterator More...
 
template<class IteratorType , typename std::enable_if< std::is_same< IteratorType, typename basic_json_t::iterator >::value||std::is_same< IteratorType, typename basic_json_t::const_iterator >::value, int >::type = 0>
IteratorType erase (IteratorType first, IteratorType last)
 remove elements given an iterator range More...
 
size_type erase (const typename object_t::key_type &key)
 remove element from a JSON object given a key More...
 
void erase (const size_type idx)
 remove element from a JSON array given an index More...
 

lookup

template<typename KeyT >
iterator find (KeyT &&key)
 find an element in a JSON object More...
 
template<typename KeyT >
const_iterator find (KeyT &&key) const
 find an element in a JSON object More...
 
template<typename KeyT >
size_type count (KeyT &&key) const
 returns the number of occurrences of a key in a JSON object More...
 
template<typename KeyT , typename std::enable_if< !std::is_same< typename std::decay< KeyT >::type, json_pointer >::value, int >::type = 0>
bool contains (KeyT &&key) const
 check the existence of an element in a JSON object More...
 
bool contains (const json_pointer &ptr) const
 check the existence of an element in a JSON object given a JSON pointer More...
 

iterators

static iteration_proxy< iteratoriterator_wrapper (reference ref) noexcept
 wrapper to access iterator member functions in range-based for More...
 
static iteration_proxy< const_iteratoriterator_wrapper (const_reference ref) noexcept
 wrapper to access iterator member functions in range-based for More...
 
iterator begin () noexcept
 returns an iterator to the first element More...
 
const_iterator begin () const noexcept
 returns a const iterator to the first element More...
 
const_iterator cbegin () const noexcept
 returns a const iterator to the first element More...
 
iterator end () noexcept
 returns an iterator to one past the last element More...
 
const_iterator end () const noexcept
 returns a const iterator to one past the last element More...
 
const_iterator cend () const noexcept
 returns a const iterator to one past the last element More...
 
reverse_iterator rbegin () noexcept
 returns an iterator to the reverse-beginning More...
 
const_reverse_iterator rbegin () const noexcept
 returns a const reverse iterator to the last element More...
 
reverse_iterator rend () noexcept
 returns an iterator to the reverse-end More...
 
const_reverse_iterator rend () const noexcept
 returns a const reverse iterator to one before the first More...
 
const_reverse_iterator crbegin () const noexcept
 returns a const reverse iterator to the last element More...
 
const_reverse_iterator crend () const noexcept
 returns a const reverse iterator to one before the first More...
 
iteration_proxy< iteratoritems () noexcept
 helper to access iterator member functions in range-based for More...
 
iteration_proxy< const_iteratoritems () const noexcept
 helper to access iterator member functions in range-based for More...
 

capacity

bool empty () const noexcept
 checks whether the container is empty. More...
 
size_type size () const noexcept
 returns the number of elements More...
 
size_type max_size () const noexcept
 returns the maximum possible number of elements More...
 

modifiers

void swap (reference left, reference right) noexcept(std::is_nothrow_move_constructible< value_t >::value &&std::is_nothrow_move_assignable< value_t >::value &&std::is_nothrow_move_constructible< json_value >::value &&std::is_nothrow_move_assignable< json_value >::value)
 exchanges the values More...
 
void clear () noexcept
 clears the contents More...
 
void push_back (basic_json &&val)
 add an object to an array More...
 
reference operator+= (basic_json &&val)
 add an object to an array More...
 
void push_back (const basic_json &val)
 add an object to an array More...
 
reference operator+= (const basic_json &val)
 add an object to an array More...
 
void push_back (const typename object_t::value_type &val)
 add an object to an object More...
 
reference operator+= (const typename object_t::value_type &val)
 add an object to an object More...
 
void push_back (initializer_list_t init)
 add an object to an object More...
 
reference operator+= (initializer_list_t init)
 add an object to an object More...
 
template<class... Args>
reference emplace_back (Args &&... args)
 add an object to an array More...
 
template<class... Args>
std::pair< iterator, bool > emplace (Args &&... args)
 add an object to an object if key does not exist More...
 
template<typename... Args>
iterator insert_iterator (const_iterator pos, Args &&... args)
 
iterator insert (const_iterator pos, const basic_json &val)
 inserts element More...
 
iterator insert (const_iterator pos, basic_json &&val)
 inserts element More...
 
iterator insert (const_iterator pos, size_type cnt, const basic_json &val)
 inserts elements More...
 
iterator insert (const_iterator pos, const_iterator first, const_iterator last)
 inserts elements More...
 
iterator insert (const_iterator pos, initializer_list_t ilist)
 inserts elements More...
 
void insert (const_iterator first, const_iterator last)
 inserts elements More...
 
void update (const_reference j)
 updates a JSON object from another object, overwriting existing keys More...
 
void update (const_iterator first, const_iterator last)
 updates a JSON object from another object, overwriting existing keys More...
 
void swap (reference other) noexcept(std::is_nothrow_move_constructible< value_t >::value &&std::is_nothrow_move_assignable< value_t >::value &&std::is_nothrow_move_constructible< json_value >::value &&std::is_nothrow_move_assignable< json_value >::value)
 exchanges the values More...
 
void swap (array_t &other)
 exchanges the values More...
 
void swap (object_t &other)
 exchanges the values More...
 
void swap (string_t &other)
 exchanges the values More...
 
void swap (binary_t &other)
 exchanges the values More...
 
void swap (typename binary_t::container_type &other)
 exchanges the values More...
 

lexicographical comparison operators

bool operator== (const_reference lhs, const_reference rhs) noexcept
 comparison: equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator== (const_reference lhs, ScalarType rhs) noexcept
 comparison: equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator== (ScalarType lhs, const_reference rhs) noexcept
 comparison: equal More...
 
bool operator!= (const_reference lhs, const_reference rhs) noexcept
 comparison: not equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator!= (const_reference lhs, ScalarType rhs) noexcept
 comparison: not equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator!= (ScalarType lhs, const_reference rhs) noexcept
 comparison: not equal More...
 
bool operator< (const_reference lhs, const_reference rhs) noexcept
 comparison: less than More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator< (const_reference lhs, ScalarType rhs) noexcept
 comparison: less than More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator< (ScalarType lhs, const_reference rhs) noexcept
 comparison: less than More...
 
bool operator<= (const_reference lhs, const_reference rhs) noexcept
 comparison: less than or equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator<= (const_reference lhs, ScalarType rhs) noexcept
 comparison: less than or equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator<= (ScalarType lhs, const_reference rhs) noexcept
 comparison: less than or equal More...
 
bool operator> (const_reference lhs, const_reference rhs) noexcept
 comparison: greater than More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator> (const_reference lhs, ScalarType rhs) noexcept
 comparison: greater than More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator> (ScalarType lhs, const_reference rhs) noexcept
 comparison: greater than More...
 
bool operator>= (const_reference lhs, const_reference rhs) noexcept
 comparison: greater than or equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator>= (const_reference lhs, ScalarType rhs) noexcept
 comparison: greater than or equal More...
 
template<typename ScalarType , typename std::enable_if< std::is_scalar< ScalarType >::value, int >::type = 0>
bool operator>= (ScalarType lhs, const_reference rhs) noexcept
 comparison: greater than or equal More...
 

serialization

std::ostream & operator<< (std::ostream &o, const basic_json &j)
 serialize to stream More...
 
std::ostream & operator>> (const basic_json &j, std::ostream &o)
 serialize to stream More...
 

deserialization

std::istream & operator<< (basic_json &j, std::istream &i)
 deserialize from stream More...
 
std::istream & operator>> (std::istream &i, basic_json &j)
 deserialize from stream More...
 
template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json parse (InputType &&i, const parser_callback_t cb=nullptr, const bool allow_exceptions=true, const bool ignore_comments=false)
 deserialize from a compatible input More...
 
template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json parse (IteratorType first, IteratorType last, const parser_callback_t cb=nullptr, const bool allow_exceptions=true, const bool ignore_comments=false)
 deserialize from a pair of character iterators More...
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json parse (detail::span_input_adapter &&i, const parser_callback_t cb=nullptr, const bool allow_exceptions=true, const bool ignore_comments=false)
 
template<typename InputType >
static bool accept (InputType &&i, const bool ignore_comments=false)
 check if the input is valid JSON More...
 
template<typename IteratorType >
static bool accept (IteratorType first, IteratorType last, const bool ignore_comments=false)
 
static JSON_HEDLEY_WARN_UNUSED_RESULT bool accept (detail::span_input_adapter &&i, const bool ignore_comments=false)
 
template<typename InputType , typename SAX >
static bool sax_parse (InputType &&i, SAX *sax, input_format_t format=input_format_t::json, const bool strict=true, const bool ignore_comments=false)
 generate SAX events More...
 
template<class IteratorType , class SAX >
static bool sax_parse (IteratorType first, IteratorType last, SAX *sax, input_format_t format=input_format_t::json, const bool strict=true, const bool ignore_comments=false)
 
template<typename SAX >
static bool sax_parse (detail::span_input_adapter &&i, SAX *sax, input_format_t format=input_format_t::json, const bool strict=true, const bool ignore_comments=false)
 

binary serialization/deserialization support

static std::vector< std::uint8_t > to_cbor (const basic_json &j)
 create a CBOR serialization of a given JSON value More...
 
static void to_cbor (const basic_json &j, detail::output_adapter< std::uint8_t > o)
 
static void to_cbor (const basic_json &j, detail::output_adapter< char > o)
 
static std::vector< std::uint8_t > to_msgpack (const basic_json &j)
 create a MessagePack serialization of a given JSON value More...
 
static void to_msgpack (const basic_json &j, detail::output_adapter< std::uint8_t > o)
 
static void to_msgpack (const basic_json &j, detail::output_adapter< char > o)
 
static std::vector< std::uint8_t > to_ubjson (const basic_json &j, const bool use_size=false, const bool use_type=false)
 create a UBJSON serialization of a given JSON value More...
 
static void to_ubjson (const basic_json &j, detail::output_adapter< std::uint8_t > o, const bool use_size=false, const bool use_type=false)
 
static void to_ubjson (const basic_json &j, detail::output_adapter< char > o, const bool use_size=false, const bool use_type=false)
 
static std::vector< std::uint8_t > to_bson (const basic_json &j)
 Serializes the given JSON object j to BSON and returns a vector containing the corresponding BSON-representation. More...
 
static void to_bson (const basic_json &j, detail::output_adapter< std::uint8_t > o)
 Serializes the given JSON object j to BSON and forwards the corresponding BSON-representation to the given output_adapter o. More...
 
static void to_bson (const basic_json &j, detail::output_adapter< char > o)
 Serializes the given JSON object j to BSON and forwards the corresponding BSON-representation to the given output_adapter o. More...
 
template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_cbor (InputType &&i, const bool strict=true, const bool allow_exceptions=true, const cbor_tag_handler_t tag_handler=cbor_tag_handler_t::error)
 create a JSON value from an input in CBOR format More...
 
template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_cbor (IteratorType first, IteratorType last, const bool strict=true, const bool allow_exceptions=true, const cbor_tag_handler_t tag_handler=cbor_tag_handler_t::error)
 create a JSON value from an input in CBOR format More...
 
template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_cbor (const T *ptr, std::size_t len, const bool strict=true, const bool allow_exceptions=true, const cbor_tag_handler_t tag_handler=cbor_tag_handler_t::error)
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_cbor (detail::span_input_adapter &&i, const bool strict=true, const bool allow_exceptions=true, const cbor_tag_handler_t tag_handler=cbor_tag_handler_t::error)
 
template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_msgpack (InputType &&i, const bool strict=true, const bool allow_exceptions=true)
 create a JSON value from an input in MessagePack format More...
 
template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_msgpack (IteratorType first, IteratorType last, const bool strict=true, const bool allow_exceptions=true)
 create a JSON value from an input in MessagePack format More...
 
template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_msgpack (const T *ptr, std::size_t len, const bool strict=true, const bool allow_exceptions=true)
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_msgpack (detail::span_input_adapter &&i, const bool strict=true, const bool allow_exceptions=true)
 
template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_ubjson (InputType &&i, const bool strict=true, const bool allow_exceptions=true)
 create a JSON value from an input in UBJSON format More...
 
template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_ubjson (IteratorType first, IteratorType last, const bool strict=true, const bool allow_exceptions=true)
 create a JSON value from an input in UBJSON format More...
 
template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_ubjson (const T *ptr, std::size_t len, const bool strict=true, const bool allow_exceptions=true)
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_ubjson (detail::span_input_adapter &&i, const bool strict=true, const bool allow_exceptions=true)
 
template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_bson (InputType &&i, const bool strict=true, const bool allow_exceptions=true)
 Create a JSON value from an input in BSON format. More...
 
template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_bson (IteratorType first, IteratorType last, const bool strict=true, const bool allow_exceptions=true)
 Create a JSON value from an input in BSON format. More...
 
template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_bson (const T *ptr, std::size_t len, const bool strict=true, const bool allow_exceptions=true)
 
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json from_bson (detail::span_input_adapter &&i, const bool strict=true, const bool allow_exceptions=true)
 

JSON Pointer functions

reference operator[] (const json_pointer &ptr)
 access specified element via JSON Pointer More...
 
const_reference operator[] (const json_pointer &ptr) const
 access specified element via JSON Pointer More...
 
reference at (const json_pointer &ptr)
 access specified element via JSON Pointer More...
 
const_reference at (const json_pointer &ptr) const
 access specified element via JSON Pointer More...
 
basic_json flatten () const
 return flattened JSON value More...
 
basic_json unflatten () const
 unflatten a previously flattened JSON value More...
 

JSON Patch functions

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json diff (const basic_json &source, const basic_json &target, const std::string &path="")
 creates a diff as a JSON patch More...
 
basic_json patch (const basic_json &json_patch) const
 applies a JSON patch More...
 

JSON Merge Patch functions

void merge_patch (const basic_json &apply_patch)
 applies a JSON Merge Patch More...
 

Detailed Description

a class to store JSON values

Template Parameters
ObjectTypetype for JSON objects (std::map by default; will be used in object_t)
ArrayTypetype for JSON arrays (std::vector by default; will be used in array_t)
StringTypetype for JSON strings and object keys (std::string by default; will be used in string_t)
BooleanTypetype for JSON booleans (bool by default; will be used in boolean_t)
NumberIntegerTypetype for JSON integer numbers (int64_t by default; will be used in number_integer_t)
NumberUnsignedTypetype for JSON unsigned integer numbers (uint64_t by default; will be used in number_unsigned_t)
NumberFloatTypetype for JSON floating-point numbers (double by default; will be used in number_float_t)
BinaryTypetype for packed binary data for compatibility with binary serialization formats (std::vector<std::uint8_t> by default; will be used in binary_t)
AllocatorTypetype of the allocator to use (std::allocator by default)
JSONSerializerthe serializer to resolve internal calls to to_json() and from_json() (adl_serializer by default)

@requirement The class satisfies the following concept requirements:

Invariant
The member variables m_value and m_type have the following relationship:
Note
ObjectType trick from https://stackoverflow.com/a/9860911
See also
RFC 8259: The JavaScript Object Notation (JSON) Data Interchange Format
Since
version 1.0.0

Definition at line 3380 of file json.hpp.

Member Typedef Documentation

◆ allocator_type

the allocator type

Definition at line 17681 of file json.hpp.

◆ array_t

using nlohmann::basic_json::array_t = ArrayType<basic_json, AllocatorType<basic_json> >

a type for an array

RFC 8259 describes JSON arrays as follows:

An array is an ordered sequence of zero or more values.

To store objects in C++, a type is defined by the template parameters explained below.

Template Parameters
ArrayTypecontainer type to store arrays (e.g., std::vector or std::list)
AllocatorTypeallocator to use for arrays (e.g., std::allocator)

Default type

With the default values for ArrayType (std::vector) and AllocatorType (std::allocator), the default value for array_t is:

std::vector<
basic_json, // value_type
std::allocator<basic_json> // allocator_type
>

Limits

RFC 8259 specifies:

An implementation may set limits on the maximum depth of nesting.

In this class, the array's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON array.

Storage

Arrays are stored as pointers in a basic_json type. That is, for any access to array values, a pointer of type array_t* must be dereferenced.

See also
see object_ttype for an object value
Since
version 1.0.0

Definition at line 17941 of file json.hpp.

◆ basic_json_t

workaround type for MSVC

Definition at line 17579 of file json.hpp.

◆ binary_reader

template<typename InputType >
using nlohmann::basic_json::binary_reader = ::nlohmann::detail::binary_reader<basic_json, InputType>
private

Definition at line 17611 of file json.hpp.

◆ binary_t

a type for a packed binary type

This type is a type designed to carry binary data that appears in various serialized formats, such as CBOR's Major Type 2, MessagePack's bin, and BSON's generic binary subtype. This type is NOT a part of standard JSON and exists solely for compatibility with these binary types. As such, it is simply defined as an ordered sequence of zero or more byte values.

Additionally, as an implementation detail, the subtype of the binary data is carried around as a std::uint8_t, which is compatible with both of the binary data formats that use binary subtyping, (though the specific numbering is incompatible with each other, and it is up to the user to translate between them).

CBOR's RFC 7049 describes this type as:

Major type 2: a byte string. The string's length in bytes is represented following the rules for positive integers (major type 0).

MessagePack's documentation on the bin type family describes this type as:

Bin format family stores an byte array in 2, 3, or 5 bytes of extra bytes in addition to the size of the byte array.

BSON's specifications describe several binary types; however, this type is intended to represent the generic binary type which has the description:

Generic binary subtype - This is the most commonly used binary subtype and should be the 'default' for drivers and tools.

None of these impose any limitations on the internal representation other than the basic unit of storage be some type of array whose parts are decomposable into bytes.

The default representation of this binary format is a std::vector<std::uint8_t>, which is a very common way to represent a byte array in modern C++.

Default type

The default values for BinaryType is std::vector<std::uint8_t>

Storage

Binary Arrays are stored as pointers in a basic_json type. That is, for any access to array values, a pointer of the type binary_t* must be dereferenced.

Notes on subtypes

  • CBOR
    • Binary values are represented as byte strings. Subtypes are serialized as tagged values.
  • MessagePack
    • If a subtype is given and the binary array contains exactly 1, 2, 4, 8, or 16 elements, the fixext family (fixext1, fixext2, fixext4, fixext8) is used. For other sizes, the ext family (ext8, ext16, ext32) is used. The subtype is then added as singed 8-bit integer.
    • If no subtype is given, the bin family (bin8, bin16, bin32) is used.
  • BSON
    • If a subtype is given, it is used and added as unsigned 8-bit integer.
    • If no subtype is given, the generic binary subtype 0x00 is used.
See also
see binarycreate a binary array
Since
version 3.8.0

Definition at line 18302 of file json.hpp.

◆ binary_writer

template<typename CharType >
using nlohmann::basic_json::binary_writer = ::nlohmann::detail::binary_writer<basic_json, CharType>
private

Definition at line 17612 of file json.hpp.

◆ boolean_t

using nlohmann::basic_json::boolean_t = BooleanType

a type for a boolean

RFC 8259 implicitly describes a boolean as a type which differentiates the two literals true and false.

To store objects in C++, a type is defined by the template parameter BooleanType which chooses the type to use.

Default type

With the default values for BooleanType (bool), the default value for boolean_t is:

bool

Storage

Boolean values are stored directly inside a basic_json type.

Since
version 1.0.0

Definition at line 18020 of file json.hpp.

◆ cbor_tag_handler_t

how to treat CBOR tags

Definition at line 17626 of file json.hpp.

◆ const_iterator

a const iterator for a basic_json container

Definition at line 17691 of file json.hpp.

◆ const_pointer

using nlohmann::basic_json::const_pointer = typename std::allocator_traits<allocator_type>::const_pointer

the type of an element const pointer

Definition at line 17686 of file json.hpp.

◆ const_reference

the type of an element const reference

Definition at line 17673 of file json.hpp.

◆ const_reverse_iterator

a const reverse iterator for a basic_json container

Definition at line 17695 of file json.hpp.

◆ difference_type

using nlohmann::basic_json::difference_type = std::ptrdiff_t

a type to represent differences between iterators

Definition at line 17676 of file json.hpp.

◆ error_handler_t

how to treat decoding errors

Definition at line 17624 of file json.hpp.

◆ exception

general exception of the basic_json class

This class is an extension of std::exception objects with a member id for exception ids. It is used as the base class for all exceptions thrown by the basic_json class. This class can hence be used as "wildcard" to catch exceptions.

Subclasses:

  • parse_error for exceptions indicating a parse error
  • invalid_iterator for exceptions indicating errors with iterators
  • type_error for exceptions indicating executing a member function with a wrong type
  • out_of_range for exceptions indicating access out of the defined range
  • other_error for exceptions indicating other library errors
Note
To have nothrow-copy-constructible exceptions, we internally use std::runtime_error which can cope with arbitrary-length error messages. Intermediate strings are built with static functions and then passed to the actual constructor.

@liveexample{The following code shows how arbitrary library exceptions can be caught.,exception}

Since
version 3.0.0

Definition at line 17643 of file json.hpp.

◆ initializer_list_t

helper type for initializer lists of basic_json values

Definition at line 17628 of file json.hpp.

◆ input_format_t

◆ internal_iterator

template<typename BasicJsonType >
using nlohmann::basic_json::internal_iterator = ::nlohmann::detail::internal_iterator<BasicJsonType>
private

Definition at line 17600 of file json.hpp.

◆ invalid_iterator

exception indicating errors with iterators

This exception is thrown if iterators passed to a library function do not match the expected semantics.

Exceptions have ids 2xx.

name / id example message description
json.exception.invalid_iterator.201 iterators are not compatible The iterators passed to constructor basic_json(InputIT first, InputIT last) are not compatible, meaning they do not belong to the same container. Therefore, the range (first, last) is invalid.
json.exception.invalid_iterator.202 iterator does not fit current value In an erase or insert function, the passed iterator pos does not belong to the JSON value for which the function was called. It hence does not define a valid position for the deletion/insertion.
json.exception.invalid_iterator.203 iterators do not fit current value Either iterator passed to function erase(IteratorType first, IteratorType last) does not belong to the JSON value from which values shall be erased. It hence does not define a valid range to delete values from.
json.exception.invalid_iterator.204 iterators out of range When an iterator range for a primitive type (number, boolean, or string) is passed to a constructor or an erase function, this range has to be exactly (begin(), end()), because this is the only way the single stored value is expressed. All other ranges are invalid.
json.exception.invalid_iterator.205 iterator out of range When an iterator for a primitive type (number, boolean, or string) is passed to an erase function, the iterator has to be the begin() iterator, because it is the only way to address the stored value. All other iterators are invalid.
json.exception.invalid_iterator.206 cannot construct with iterators from null The iterators passed to constructor basic_json(InputIT first, InputIT last) belong to a JSON null value and hence to not define a valid range.
json.exception.invalid_iterator.207 cannot use key() for non-object iterators The key() member function can only be used on iterators belonging to a JSON object, because other types do not have a concept of a key.
json.exception.invalid_iterator.208 cannot use operator[] for object iterators The operator[] to specify a concrete offset cannot be used on iterators belonging to a JSON object, because JSON objects are unordered.
json.exception.invalid_iterator.209 cannot use offsets with object iterators The offset operators (+, -, +=, -=) cannot be used on iterators belonging to a JSON object, because JSON objects are unordered.
json.exception.invalid_iterator.210 iterators do not fit The iterator range passed to the insert function are not compatible, meaning they do not belong to the same container. Therefore, the range (first, last) is invalid.
json.exception.invalid_iterator.211 passed iterators may not belong to container The iterator range passed to the insert function must not be a subrange of the container to insert to.
json.exception.invalid_iterator.212 cannot compare iterators of different containers When two iterators are compared, they must belong to the same container.
json.exception.invalid_iterator.213 cannot compare order of object iterators The order of object iterators cannot be compared, because JSON objects are unordered.
json.exception.invalid_iterator.214 cannot get value Cannot get value for iterator: Either the iterator belongs to a null value or it is an iterator to a primitive type (number, boolean, or string), but the iterator is different to begin().

@liveexample{The following code shows how an invalid_iterator exception can be caught.,invalid_iterator}

See also
- exception for the base class of the library exceptions
- parse_error for exceptions indicating a parse error
- type_error for exceptions indicating executing a member function with a wrong type
- out_of_range for exceptions indicating access out of the defined range
- other_error for exceptions indicating other library errors
Since
version 3.0.0

Definition at line 17647 of file json.hpp.

◆ iter_impl

template<typename BasicJsonType >
using nlohmann::basic_json::iter_impl = ::nlohmann::detail::iter_impl<BasicJsonType>
private

Definition at line 17602 of file json.hpp.

◆ iteration_proxy

template<typename Iterator >
using nlohmann::basic_json::iteration_proxy = ::nlohmann::detail::iteration_proxy<Iterator>
private

Definition at line 17604 of file json.hpp.

◆ iterator

an iterator for a basic_json container

Definition at line 17689 of file json.hpp.

◆ json_pointer

◆ json_reverse_iterator

Definition at line 17605 of file json.hpp.

◆ json_sax_t

SAX interface type, see nlohmann::json_sax.

Definition at line 17632 of file json.hpp.

◆ json_serializer

template<typename T , typename SFINAE >
using nlohmann::basic_json::json_serializer = JSONSerializer<T, SFINAE>

Definition at line 17622 of file json.hpp.

◆ number_float_t

using nlohmann::basic_json::number_float_t = NumberFloatType

a type for a number (floating-point)

RFC 8259 describes numbers as follows:

The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.

This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t and number_float_t are used.

To store floating-point numbers in C++, a type is defined by the template parameter NumberFloatType which chooses the type to use.

Default type

With the default values for NumberFloatType (double), the default value for number_float_t is:

double

Default behavior

  • The restrictions about leading zeros is not enforced in C++. Instead, leading zeros in floating-point literals will be ignored. Internally, the value will be stored as decimal number. For instance, the C++ floating-point literal 01.2 will be serialized to 1.2. During deserialization, leading zeros yield an error.
  • Not-a-number (NaN) values will be serialized to null.

Limits

RFC 8259 states:

This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision.

This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note values smaller than -1.79769313486232e+308 and values greater than 1.79769313486232e+308 will be stored as NaN internally and be serialized to null.

Storage

Floating-point number values are stored directly inside a basic_json type.

See also
see number_integer_ttype for number values (integer)
see number_unsigned_ttype for number values (unsigned integer)
Since
version 1.0.0

Definition at line 18231 of file json.hpp.

◆ number_integer_t

using nlohmann::basic_json::number_integer_t = NumberIntegerType

a type for a number (integer)

RFC 8259 describes numbers as follows:

The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.

This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t and number_float_t are used.

To store integer numbers in C++, a type is defined by the template parameter NumberIntegerType which chooses the type to use.

Default type

With the default values for NumberIntegerType (int64_t), the default value for number_integer_t is:

int64_t

Default behavior

  • The restrictions about leading zeros is not enforced in C++. Instead, leading zeros in integer literals lead to an interpretation as octal number. Internally, the value will be stored as decimal number. For instance, the C++ integer literal 010 will be serialized to 8. During deserialization, leading zeros yield an error.
  • Not-a-number (NaN) values will be serialized to null.

Limits

RFC 8259 specifies:

An implementation may set limits on the range and precision of numbers.

When the default type is used, the maximal integer number that can be stored is 9223372036854775807 (INT64_MAX) and the minimal integer number that can be stored is -9223372036854775808 (INT64_MIN). Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will be automatically be stored as number_unsigned_t or number_float_t.

RFC 8259 further states:

Note that when such software is used, numbers that are integers and are in the range $[-2^{53}+1, 2^{53}-1]$ are interoperable in the sense that implementations will agree exactly on their numeric values.

As this range is a subrange of the exactly supported range [INT64_MIN, INT64_MAX], this class's integer type is interoperable.

Storage

Integer number values are stored directly inside a basic_json type.

See also
see number_float_ttype for number values (floating-point)
see number_unsigned_ttype for number values (unsigned integer)
Since
version 1.0.0

Definition at line 18092 of file json.hpp.

◆ number_unsigned_t

using nlohmann::basic_json::number_unsigned_t = NumberUnsignedType

a type for a number (unsigned)

RFC 8259 describes numbers as follows:

The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.

This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t and number_float_t are used.

To store unsigned integer numbers in C++, a type is defined by the template parameter NumberUnsignedType which chooses the type to use.

Default type

With the default values for NumberUnsignedType (uint64_t), the default value for number_unsigned_t is:

uint64_t

Default behavior

  • The restrictions about leading zeros is not enforced in C++. Instead, leading zeros in integer literals lead to an interpretation as octal number. Internally, the value will be stored as decimal number. For instance, the C++ integer literal 010 will be serialized to 8. During deserialization, leading zeros yield an error.
  • Not-a-number (NaN) values will be serialized to null.

Limits

RFC 8259 specifies:

An implementation may set limits on the range and precision of numbers.

When the default type is used, the maximal integer number that can be stored is 18446744073709551615 (UINT64_MAX) and the minimal integer number that can be stored is 0. Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will be automatically be stored as number_integer_t or number_float_t.

RFC 8259 further states:

Note that when such software is used, numbers that are integers and are in the range $[-2^{53}+1, 2^{53}-1]$ are interoperable in the sense that implementations will agree exactly on their numeric values.

As this range is a subrange (when considered in conjunction with the number_integer_t type) of the exactly supported range [0, UINT64_MAX], this class's integer type is interoperable.

Storage

Integer number values are stored directly inside a basic_json type.

See also
see number_float_ttype for number values (floating-point)
see number_integer_ttype for number values (integer)
Since
version 2.0.0

Definition at line 18163 of file json.hpp.

◆ object_comparator_t

using nlohmann::basic_json::object_comparator_t = std::less<StringType>

Definition at line 17805 of file json.hpp.

◆ object_t

using nlohmann::basic_json::object_t = ObjectType<StringType, basic_json, object_comparator_t, AllocatorType<std::pair<const StringType, basic_json> >>

a type for an object

RFC 8259 describes JSON objects as follows:

An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a string, number, boolean, null, object, or array.

To store objects in C++, a type is defined by the template parameters described below.

Template Parameters
ObjectTypethe container to store objects (e.g., std::map or std::unordered_map)
StringTypethe type of the keys or names (e.g., std::string). The comparison function std::less<StringType> is used to order elements inside the container.
AllocatorTypethe allocator to use for objects (e.g., std::allocator)

Default type

With the default values for ObjectType (std::map), StringType (std::string), and AllocatorType (std::allocator), the default value for object_t is:

std::string, // key_type
basic_json, // value_type
std::less<std::string>, // key_compare
std::allocator<std::pair<const std::string, basic_json>> // allocator_type
>

Behavior

The choice of object_t influences the behavior of the JSON class. With the default type, objects have the following behavior:

  • When all names are unique, objects will be interoperable in the sense that all software implementations receiving that object will agree on the name-value mappings.
  • When the names within an object are not unique, it is unspecified which one of the values for a given key will be chosen. For instance, {"key": 2, "key": 1} could be equal to either {"key": 1} or {"key": 2}.
  • Internally, name/value pairs are stored in lexicographical order of the names. Objects will also be serialized (see dump) in this order. For instance, {"b": 1, "a": 2} and {"a": 2, "b": 1} will be stored and serialized as {"a": 2, "b": 1}.
  • When comparing objects, the order of the name/value pairs is irrelevant. This makes objects interoperable in the sense that they will not be affected by these differences. For instance, {"b": 1, "a": 2} and {"a": 2, "b": 1} will be treated as equal.

Limits

RFC 8259 specifies:

An implementation may set limits on the maximum depth of nesting.

In this class, the object's limit of nesting is not explicitly constrained. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON object.

Storage

Objects are stored as pointers in a basic_json type. That is, for any access to object values, a pointer of type object_t* must be dereferenced.

See also
see array_ttype for an array value
Since
version 1.0.0
Note
The order name/value pairs are added to the object is not preserved by the library. Therefore, iterating an object may return name/value pairs in a different order than they were originally stored. In fact, keys will be traversed in alphabetical order as std::map with std::less is used by default. Please note this behavior conforms to RFC 8259, because any order implements the specified "unordered" nature of JSON objects.

Definition at line 17895 of file json.hpp.

◆ other_error

exception indicating other library errors

This exception is thrown in case of errors that cannot be classified with the other exception types.

Exceptions have ids 5xx.

name / id example message description
json.exception.other_error.501 unsuccessful: {"op":"test","path":"/baz", "value":"bar"} A JSON Patch operation 'test' failed. The unsuccessful operation is also printed.
See also
- exception for the base class of the library exceptions
- parse_error for exceptions indicating a parse error
- invalid_iterator for exceptions indicating errors with iterators
- type_error for exceptions indicating executing a member function with a wrong type
- out_of_range for exceptions indicating access out of the defined range

@liveexample{The following code shows how an other_error exception can be caught.,other_error}

Since
version 3.0.0

Definition at line 17653 of file json.hpp.

◆ out_of_range

exception indicating access out of the defined range

This exception is thrown in case a library function is called on an input parameter that exceeds the expected range, for instance in case of array indices or nonexisting object keys.

Exceptions have ids 4xx.

name / id example message description
json.exception.out_of_range.401 array index 3 is out of range The provided array index i is larger than size-1.
json.exception.out_of_range.402 array index '-' (3) is out of range The special array index - in a JSON Pointer never describes a valid element of the array, but the index past the end. That is, it can only be used to add elements at this position, but not to read it.
json.exception.out_of_range.403 key 'foo' not found The provided key was not found in the JSON object.
json.exception.out_of_range.404 unresolved reference token 'foo' A reference token in a JSON Pointer could not be resolved.
json.exception.out_of_range.405 JSON pointer has no parent The JSON Patch operations 'remove' and 'add' can not be applied to the root element of the JSON value.
json.exception.out_of_range.406 number overflow parsing '10E1000' A parsed number could not be stored as without changing it to NaN or INF.
json.exception.out_of_range.407 number overflow serializing '9223372036854775808' UBJSON and BSON only support integer numbers up to 9223372036854775807. (until version 3.8.0)
json.exception.out_of_range.408 excessive array size: 8658170730974374167 The size (following #) of an UBJSON array or object exceeds the maximal capacity.
json.exception.out_of_range.409 BSON key cannot contain code point U+0000 (at byte 2) Key identifiers to be serialized to BSON cannot contain code point U+0000, since the key is stored as zero-terminated c-string

@liveexample{The following code shows how an out_of_range exception can be caught.,out_of_range}

See also
- exception for the base class of the library exceptions
- parse_error for exceptions indicating a parse error
- invalid_iterator for exceptions indicating errors with iterators
- type_error for exceptions indicating executing a member function with a wrong type
- other_error for exceptions indicating other library errors
Since
version 3.0.0

Definition at line 17651 of file json.hpp.

◆ output_adapter_t

template<typename CharType >
using nlohmann::basic_json::output_adapter_t = ::nlohmann::detail::output_adapter_t<CharType>
private

Definition at line 17608 of file json.hpp.

◆ parse_error

exception indicating a parse error

This exception is thrown by the library when a parse error occurs. Parse errors can occur during the deserialization of JSON text, CBOR, MessagePack, as well as when using JSON Patch.

Member byte holds the byte index of the last read character in the input file.

Exceptions have ids 1xx.

name / id example message description
json.exception.parse_error.101 parse error at 2: unexpected end of input; expected string literal This error indicates a syntax error while deserializing a JSON text. The error message describes that an unexpected token (character) was encountered, and the member byte indicates the error position.
json.exception.parse_error.102 parse error at 14: missing or wrong low surrogate JSON uses the \uxxxx format to describe Unicode characters. Code points above above 0xFFFF are split into two \uxxxx entries ("surrogate pairs"). This error indicates that the surrogate pair is incomplete or contains an invalid code point.
json.exception.parse_error.103 parse error: code points above 0x10FFFF are invalid Unicode supports code points up to 0x10FFFF. Code points above 0x10FFFF are invalid.
json.exception.parse_error.104 parse error: JSON patch must be an array of objects RFC 6902 requires a JSON Patch document to be a JSON document that represents an array of objects.
json.exception.parse_error.105 parse error: operation must have string member 'op' An operation of a JSON Patch document must contain exactly one "op" member, whose value indicates the operation to perform. Its value must be one of "add", "remove", "replace", "move", "copy", or "test"; other values are errors.
json.exception.parse_error.106 parse error: array index '01' must not begin with '0' An array index in a JSON Pointer (RFC 6901) may be 0 or any number without a leading 0.
json.exception.parse_error.107 parse error: JSON pointer must be empty or begin with '/' - was: 'foo' A JSON Pointer must be a Unicode string containing a sequence of zero or more reference tokens, each prefixed by a / character.
json.exception.parse_error.108 parse error: escape character '~' must be followed with '0' or '1' In a JSON Pointer, only ~0 and ~1 are valid escape sequences.
json.exception.parse_error.109 parse error: array index 'one' is not a number A JSON Pointer array index must be a number.
json.exception.parse_error.110 parse error at 1: cannot read 2 bytes from vector When parsing CBOR or MessagePack, the byte vector ends before the complete value has been read.
json.exception.parse_error.112 parse error at 1: error reading CBOR; last byte: 0xF8 Not all types of CBOR or MessagePack are supported. This exception occurs if an unsupported byte was read.
json.exception.parse_error.113 parse error at 2: expected a CBOR string; last byte: 0x98 While parsing a map key, a value that is not a string has been read.
json.exception.parse_error.114 parse error: Unsupported BSON record type 0x0F The parsing of the corresponding BSON record type is not implemented (yet).
json.exception.parse_error.115 parse error at byte 5: syntax error while parsing UBJSON high-precision number: invalid number text: 1A A UBJSON high-precision number could not be parsed.
Note
For an input with n bytes, 1 is the index of the first character and n+1 is the index of the terminating null byte or the end of file. This also holds true when reading a byte vector (CBOR or MessagePack).

@liveexample{The following code shows how a parse_error exception can be caught.,parse_error}

See also
- exception for the base class of the library exceptions
- invalid_iterator for exceptions indicating errors with iterators
- type_error for exceptions indicating executing a member function with a wrong type
- out_of_range for exceptions indicating access out of the defined range
- other_error for exceptions indicating other library errors
Since
version 3.0.0

Definition at line 17645 of file json.hpp.

◆ parse_event_t

parser event types

The parser callback distinguishes the following events:

  • object_start: the parser read { and started to process a JSON object
  • key: the parser read a key of a value in an object
  • object_end: the parser read } and finished processing a JSON object
  • array_start: the parser read [ and started to process a JSON array
  • array_end: the parser read ] and finished processing a JSON array
  • value: the parser finished reading a JSON value
Example when certain parse events are triggered
See also
see parser_callback_t for more information and examples

Definition at line 18748 of file json.hpp.

◆ parser_callback_t

per-element parser callback type

With a parser callback function, the result of parsing a JSON text can be influenced. When passed to parse, it is called on certain events (passed as parse_event_t via parameter event) with a set recursion depth depth and context JSON value parsed. The return value of the callback function is a boolean indicating whether the element that emitted the callback shall be kept or not.

We distinguish six scenarios (determined by the event type) in which the callback function can be called. The following table describes the values of the parameters depth, event, and parsed.

parameter event description parameter depth parameter parsed
parse_event_t::object_start the parser read { and started to process a JSON object depth of the parent of the JSON object a JSON value with type discarded
parse_event_t::key the parser read a key of a value in an object depth of the currently parsed JSON object a JSON string containing the key
parse_event_t::object_end the parser read } and finished processing a JSON object depth of the parent of the JSON object the parsed JSON object
parse_event_t::array_start the parser read [ and started to process a JSON array depth of the parent of the JSON array a JSON value with type discarded
parse_event_t::array_end the parser read ] and finished processing a JSON array depth of the parent of the JSON array the parsed JSON array
parse_event_t::value the parser finished reading a JSON value depth of the value the parsed JSON value
Example when certain parse events are triggered

Discarding a value (i.e., returning false) has different effects depending on the context in which function was called:

  • Discarded values in structured types are skipped. That is, the parser will behave as if the discarded value was never read.
  • In case a value outside a structured type is skipped, it is replaced with null. This case happens if the top-level element is skipped.
Parameters
[in]depththe depth of the recursion during parsing
[in]eventan event of type parse_event_t indicating the context in the callback function has been called
[in,out]parsedthe current intermediate parse result; note that writing to this value has no effect for parse_event_t::key events
Returns
Whether the JSON value which called the function during parsing should be kept (true) or not (false). In the latter case, it is either skipped completely or replaced by an empty discarded object.
See also
see parse for examples
Since
version 1.0.0

Definition at line 18799 of file json.hpp.

◆ pointer

using nlohmann::basic_json::pointer = typename std::allocator_traits<allocator_type>::pointer

the type of an element pointer

Definition at line 17684 of file json.hpp.

◆ primitive_iterator_t

◆ reference

the type of an element reference

Definition at line 17671 of file json.hpp.

◆ reverse_iterator

a reverse iterator for a basic_json container

Definition at line 17693 of file json.hpp.

◆ size_type

using nlohmann::basic_json::size_type = std::size_t

a type to represent container sizes

Definition at line 17678 of file json.hpp.

◆ string_t

using nlohmann::basic_json::string_t = StringType

a type for a string

RFC 8259 describes JSON strings as follows:

A string is a sequence of zero or more Unicode characters.

To store objects in C++, a type is defined by the template parameter described below. Unicode values are split by the JSON class into byte-sized characters during deserialization.

Template Parameters
StringTypethe container to store strings (e.g., std::string). Note this container is used for keys/names in objects, see object_t.

Default type

With the default values for StringType (std::string), the default value for string_t is:

std::string

Encoding

Strings are stored in UTF-8 encoding. Therefore, functions like std::string::size() or std::string::length() return the number of bytes in the string rather than the number of characters or glyphs.

String comparison

RFC 8259 states:

Software implementations are typically required to test names of object members for equality. Implementations that transform the textual representation into sequences of Unicode code units and then perform the comparison numerically, code unit by code unit, are interoperable in the sense that implementations will agree in all cases on equality or inequality of two strings. For example, implementations that compare strings with escaped characters unconverted may incorrectly find that "a\\b" and "a\u005Cb" are not equal.

This implementation is interoperable as it does compare strings code unit by code unit.

Storage

String values are stored as pointers in a basic_json type. That is, for any access to string values, a pointer of type string_t* must be dereferenced.

Since
version 1.0.0

Definition at line 17994 of file json.hpp.

◆ type_error

exception indicating executing a member function with a wrong type

This exception is thrown in case of a type error; that is, a library function is executed on a JSON value whose type does not match the expected semantics.

Exceptions have ids 3xx.

name / id example message description
json.exception.type_error.301 cannot create object from initializer list To create an object from an initializer list, the initializer list must consist only of a list of pairs whose first element is a string. When this constraint is violated, an array is created instead.
json.exception.type_error.302 type must be object, but is array During implicit or explicit value conversion, the JSON type must be compatible to the target type. For instance, a JSON string can only be converted into string types, but not into numbers or boolean types.
json.exception.type_error.303 incompatible ReferenceType for get_ref, actual type is object To retrieve a reference to a value stored in a basic_json object with get_ref, the type of the reference must match the value type. For instance, for a JSON array, the ReferenceType must be array_t &.
json.exception.type_error.304 cannot use at() with string The at() member functions can only be executed for certain JSON types.
json.exception.type_error.305 cannot use operator[] with string The operator[] member functions can only be executed for certain JSON types.
json.exception.type_error.306 cannot use value() with string The value() member functions can only be executed for certain JSON types.
json.exception.type_error.307 cannot use erase() with string The erase() member functions can only be executed for certain JSON types.
json.exception.type_error.308 cannot use push_back() with string The push_back() and operator+= member functions can only be executed for certain JSON types.
json.exception.type_error.309 cannot use insert() with The insert() member functions can only be executed for certain JSON types.
json.exception.type_error.310 cannot use swap() with number The swap() member functions can only be executed for certain JSON types.
json.exception.type_error.311 cannot use emplace_back() with string The emplace_back() member function can only be executed for certain JSON types.
json.exception.type_error.312 cannot use update() with string The update() member functions can only be executed for certain JSON types.
json.exception.type_error.313 invalid value to unflatten The unflatten function converts an object whose keys are JSON Pointers back into an arbitrary nested JSON value. The JSON Pointers must not overlap, because then the resulting value would not be well defined.
json.exception.type_error.314 only objects can be unflattened The unflatten function only works for an object whose keys are JSON Pointers.
json.exception.type_error.315 values in object must be primitive The unflatten function only works for an object whose keys are JSON Pointers and whose values are primitive.
json.exception.type_error.316 invalid UTF-8 byte at index 10: 0x7E The dump function only works with UTF-8 encoded strings; that is, if you assign a std::string to a JSON value, make sure it is UTF-8 encoded.
json.exception.type_error.317 JSON value cannot be serialized to requested format The dynamic type of the object cannot be represented in the requested serialization format (e.g. a raw true or null JSON object cannot be serialized to BSON)

@liveexample{The following code shows how a type_error exception can be caught.,type_error}

See also
- exception for the base class of the library exceptions
- parse_error for exceptions indicating a parse error
- invalid_iterator for exceptions indicating errors with iterators
- out_of_range for exceptions indicating access out of the defined range
- other_error for exceptions indicating other library errors
Since
version 3.0.0

Definition at line 17649 of file json.hpp.

◆ value_t

Definition at line 17618 of file json.hpp.

◆ value_type

the type of elements in a basic_json container

Definition at line 17668 of file json.hpp.

Constructor & Destructor Documentation

◆ basic_json() [1/10]

nlohmann::basic_json::basic_json ( const value_t  v)
inline

create an empty value with a given type

Create an empty JSON value with a given type. The value will be default initialized with an empty value which depends on the type:

Value type initial value
null null
boolean false
string ""
number 0
object {}
array []
binary empty array
Parameters
[in]vthe type of the value to create

@complexity Constant.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

@liveexample{The following code shows the constructor for different value_t values,basic_json__value_t}

See also
see clear() – restores the postcondition of this constructor
Since
version 1.0.0

Definition at line 18840 of file json.hpp.

References assert_invariant().

Referenced by basic_json(), binary(), from_bson(), from_cbor(), from_msgpack(), from_ubjson(), json_value(), and push_back().

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◆ basic_json() [2/10]

nlohmann::basic_json::basic_json ( std::nullptr_t  = nullptr)
inlinenoexcept

create a null object

Create a null JSON value. It either takes a null pointer as parameter (explicitly creating null) or no parameter (implicitly creating null). The passed null pointer itself is not read – it is only used to choose the right constructor.

@complexity Constant.

@exceptionsafety No-throw guarantee: this constructor never throws exceptions.

@liveexample{The following code shows the constructor with and without a null pointer parameter.,basic_json__nullptr_t}

Since
version 1.0.0

Definition at line 18864 of file json.hpp.

References assert_invariant().

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◆ basic_json() [3/10]

template<typename CompatibleType , typename U = detail::uncvref_t<CompatibleType>, detail::enable_if_t< !detail::is_basic_json< U >::value &&detail::is_compatible_type< basic_json_t, U >::value, int > = 0>
nlohmann::basic_json::basic_json ( CompatibleType &&  val)
inlinenoexcept

create a JSON value

This is a "catch all" constructor for all compatible JSON types; that is, types for which a to_json() method exists. The constructor forwards the parameter val to that method (to json_serializer<U>::to_json method with U = uncvref_t<CompatibleType>, to be exact).

Template type CompatibleType includes, but is not limited to, the following types:

  • arrays: array_t and all kinds of compatible containers such as std::vector, std::deque, std::list, std::forward_list, std::array, std::valarray, std::set, std::unordered_set, std::multiset, and std::unordered_multiset with a value_type from which a basic_json value can be constructed.
  • objects: object_t and all kinds of compatible associative containers such as std::map, std::unordered_map, std::multimap, and std::unordered_multimap with a key_type compatible to string_t and a value_type from which a basic_json value can be constructed.
  • strings: string_t, string literals, and all compatible string containers can be used.
  • numbers: number_integer_t, number_unsigned_t, number_float_t, and all convertible number types such as int, size_t, int64_t, float or double can be used.
  • boolean: boolean_t / bool can be used.
  • binary: binary_t / std::vector<std::uint8_t> may be used, unfortunately because string literals cannot be distinguished from binary character arrays by the C++ type system, all types compatible with const char* will be directed to the string constructor instead. This is both for backwards compatibility, and due to the fact that a binary type is not a standard JSON type.

See the examples below.

Template Parameters
CompatibleTypea type such that:
  • CompatibleType is not derived from std::istream,
  • CompatibleType is not basic_json (to avoid hijacking copy/move constructors),
  • CompatibleType is not a different basic_json type (i.e. with different template arguments)
  • CompatibleType is not a basic_json nested type (e.g., json_pointer, iterator, etc ...)
  • json_serializer<U> has a to_json(basic_json_t&, CompatibleType&&) method
U= uncvref_t<CompatibleType>
Parameters
[in]valthe value to be forwarded to the respective constructor

@complexity Usually linear in the size of the passed val, also depending on the implementation of the called to_json() method.

@exceptionsafety Depends on the called constructor. For types directly supported by the library (i.e., all types for which no to_json() function was provided), strong guarantee holds: if an exception is thrown, there are no changes to any JSON value.

@liveexample{The following code shows the constructor with several compatible types.,basic_json__CompatibleType}

Since
version 2.1.0

Definition at line 18936 of file json.hpp.

References assert_invariant(), set_parents(), and nlohmann::detail::to_json().

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◆ basic_json() [4/10]

template<typename BasicJsonType , detail::enable_if_t< detail::is_basic_json< BasicJsonType >::value &&!std::is_same< basic_json, BasicJsonType >::value, int > = 0>
nlohmann::basic_json::basic_json ( const BasicJsonType &  val)
inline

create a JSON value from an existing one

This is a constructor for existing basic_json types. It does not hijack copy/move constructors, since the parameter has different template arguments than the current ones.

The constructor tries to convert the internal m_value of the parameter.

Template Parameters
BasicJsonTypea type such that:
Parameters
[in]valthe basic_json value to be converted.

@complexity Usually linear in the size of the passed val, also depending on the implementation of the called to_json() method.

@exceptionsafety Depends on the called constructor. For types directly supported by the library (i.e., all types for which no to_json() function was provided), strong guarantee holds: if an exception is thrown, there are no changes to any JSON value.

Since
version 3.2.0

Definition at line 18974 of file json.hpp.

References nlohmann::detail::array, assert_invariant(), nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::discarded, JSON_ASSERT, nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, set_parents(), nlohmann::detail::string, and nlohmann::detail::to_json().

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◆ basic_json() [5/10]

nlohmann::basic_json::basic_json ( initializer_list_t  init,
bool  type_deduction = true,
value_t  manual_type = value_t::array 
)
inline

create a container (array or object) from an initializer list

Creates a JSON value of type array or object from the passed initializer list init. In case type_deduction is true (default), the type of the JSON value to be created is deducted from the initializer list init according to the following rules:

  1. If the list is empty, an empty JSON object value {} is created.
  2. If the list consists of pairs whose first element is a string, a JSON object value is created where the first elements of the pairs are treated as keys and the second elements are as values.
  3. In all other cases, an array is created.

The rules aim to create the best fit between a C++ initializer list and JSON values. The rationale is as follows:

  1. The empty initializer list is written as {} which is exactly an empty JSON object.
  2. C++ has no way of describing mapped types other than to list a list of pairs. As JSON requires that keys must be of type string, rule 2 is the weakest constraint one can pose on initializer lists to interpret them as an object.
  3. In all other cases, the initializer list could not be interpreted as JSON object type, so interpreting it as JSON array type is safe.

With the rules described above, the following JSON values cannot be expressed by an initializer list:

Note
When used without parentheses around an empty initializer list, basic_json() is called instead of this function, yielding the JSON null value.
Parameters
[in]initinitializer list with JSON values
[in]type_deductioninternal parameter; when set to true, the type of the JSON value is deducted from the initializer list init; when set to false, the type provided via manual_type is forced. This mode is used by the functions array(initializer_list_t) and object(initializer_list_t).
[in]manual_typeinternal parameter; when type_deduction is set to false, the created JSON value will use the provided type (only value_t::array and value_t::object are valid); when type_deduction is set to true, this parameter has no effect
Exceptions
type_error.301if type_deduction is false, manual_type is value_t::object, but init contains an element which is not a pair whose first element is a string. In this case, the constructor could not create an object. If type_deduction would have be true, an array would have been created. See object(initializer_list_t) for an example.

@complexity Linear in the size of the initializer list init.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

@liveexample{The example below shows how JSON values are created from initializer lists.,basic_json__list_init_t}

See also
see array(initializer_list_t)create a JSON array value from an initializer list
see object(initializer_list_t)create a JSON object value from an initializer list
Since
version 1.0.0

Definition at line 19098 of file json.hpp.

References nlohmann::detail::array, assert_invariant(), basic_json(), nlohmann::detail::type_error::create(), board::element, init(), JSON_HEDLEY_UNLIKELY, JSON_THROW, m_value, nlohmann::detail::json_ref< BasicJsonType >::moved_or_copied(), nlohmann::detail::object, and set_parents().

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◆ basic_json() [6/10]

nlohmann::basic_json::basic_json ( size_type  cnt,
const basic_json val 
)
inline

construct an array with count copies of given value

Constructs a JSON array value by creating cnt copies of a passed value. In case cnt is 0, an empty array is created.

Parameters
[in]cntthe number of JSON copies of val to create
[in]valthe JSON value to copy
Postcondition
std::distance(begin(),end()) == cnt holds.

@complexity Linear in cnt.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

@liveexample{The following code shows examples for the basic_json(size_type\, const basic_json&) constructor.,basic_json__size_type_basic_json}

Since
version 1.0.0

Definition at line 19353 of file json.hpp.

References assert_invariant(), m_value, and set_parents().

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◆ basic_json() [7/10]

template<class InputIT , typename std::enable_if< std::is_same< InputIT, typename basic_json_t::iterator >::value||std::is_same< InputIT, typename basic_json_t::const_iterator >::value, int >::type = 0>
nlohmann::basic_json::basic_json ( InputIT  first,
InputIT  last 
)
inline

construct a JSON container given an iterator range

Constructs the JSON value with the contents of the range [first, last). The semantics depends on the different types a JSON value can have:

  • In case of a null type, invalid_iterator.206 is thrown.
  • In case of other primitive types (number, boolean, or string), first must be begin() and last must be end(). In this case, the value is copied. Otherwise, invalid_iterator.204 is thrown.
  • In case of structured types (array, object), the constructor behaves as similar versions for std::vector or std::map; that is, a JSON array or object is constructed from the values in the range.
Template Parameters
InputITan input iterator type (iterator or const_iterator)
Parameters
[in]firstbegin of the range to copy from (included)
[in]lastend of the range to copy from (excluded)
Precondition
Iterators first and last must be initialized. This precondition is enforced with an assertion (see warning). If assertions are switched off, a violation of this precondition yields undefined behavior.
Range [first, last) is valid. Usually, this precondition cannot be checked efficiently. Only certain edge cases are detected; see the description of the exceptions below. A violation of this precondition yields undefined behavior.
Warning
A precondition is enforced with a runtime assertion that will result in calling std::abort if this precondition is not met. Assertions can be disabled by defining NDEBUG at compile time. See https://en.cppreference.com/w/cpp/error/assert for more information.
Exceptions
invalid_iterator.201if iterators first and last are not compatible (i.e., do not belong to the same JSON value). In this case, the range [first, last) is undefined.
invalid_iterator.204if iterators first and last belong to a primitive type (number, boolean, or string), but first does not point to the first element any more. In this case, the range [first, last) is undefined. See example code below.
invalid_iterator.206if iterators first and last belong to a null value. In this case, the range [first, last) is undefined.

@complexity Linear in distance between first and last.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

@liveexample{The example below shows several ways to create JSON values by specifying a subrange with iterators.,basic_json__InputIt_InputIt}

Since
version 1.0.0

Definition at line 19419 of file json.hpp.

References nlohmann::detail::array, assert_invariant(), basic_json(), nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::invalid_iterator::create(), nlohmann::detail::discarded, JSON_ASSERT, JSON_HEDLEY_UNLIKELY, JSON_THROW, m_value, nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, set_parents(), and nlohmann::detail::string.

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◆ basic_json() [8/10]

template<typename JsonRef , detail::enable_if_t< detail::conjunction< detail::is_json_ref< JsonRef >, std::is_same< typename JsonRef::value_type, basic_json >>::value, int > = 0>
nlohmann::basic_json::basic_json ( const JsonRef &  ref)
inline

Definition at line 19529 of file json.hpp.

◆ basic_json() [9/10]

nlohmann::basic_json::basic_json ( const basic_json other)
inline

copy constructor

Creates a copy of a given JSON value.

Parameters
[in]otherthe JSON value to copy
Postcondition
*this == other

@complexity Linear in the size of other.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is linear.
  • As postcondition, it holds: other == basic_json(other).

@liveexample{The following code shows an example for the copy constructor.,basic_json__basic_json}

Since
version 1.0.0

Definition at line 19556 of file json.hpp.

References nlohmann::detail::array, assert_invariant(), nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::discarded, m_value, nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, set_parents(), and nlohmann::detail::string.

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◆ basic_json() [10/10]

nlohmann::basic_json::basic_json ( basic_json &&  other)
inlinenoexcept

move constructor

Move constructor. Constructs a JSON value with the contents of the given value other using move semantics. It "steals" the resources from other and leaves it as JSON null value.

Parameters
[in,out]othervalue to move to this object
Postcondition
*this has the same value as other before the call.
other is a JSON null value.

@complexity Constant.

@exceptionsafety No-throw guarantee: this constructor never throws exceptions.

@requirement This function helps basic_json satisfying the MoveConstructible requirements.

@liveexample{The code below shows the move constructor explicitly called via std::move.,basic_json__moveconstructor}

Since
version 1.0.0

Definition at line 19648 of file json.hpp.

References assert_invariant(), nlohmann::detail::null, and set_parents().

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◆ ~basic_json()

nlohmann::basic_json::~basic_json ( )
inlinenoexcept

destructor

Destroys the JSON value and frees all allocated memory.

@complexity Linear.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is linear.
  • All stored elements are destroyed and all memory is freed.
Since
version 1.0.0

Definition at line 19720 of file json.hpp.

References assert_invariant(), and m_value.

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Member Function Documentation

◆ accept() [1/3]

static JSON_HEDLEY_WARN_UNUSED_RESULT bool nlohmann::basic_json::accept ( detail::span_input_adapter &&  i,
const bool  ignore_comments = false 
)
inlinestatic

Definition at line 24354 of file json.hpp.

References parser().

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◆ accept() [2/3]

template<typename InputType >
static bool nlohmann::basic_json::accept ( InputType &&  i,
const bool  ignore_comments = false 
)
inlinestatic

check if the input is valid JSON

Unlike the parse(InputType&&, const parser_callback_t,const bool) function, this function neither throws an exception in case of invalid JSON input (i.e., a parse error) nor creates diagnostic information.

Template Parameters
InputTypeA compatible input, for instance
  • an std::istream object
  • a FILE pointer
  • a C-style array of characters
  • a pointer to a null-terminated string of single byte characters
  • an object obj for which begin(obj) and end(obj) produces a valid pair of iterators.
Parameters
[in]iinput to read from
[in]ignore_commentswhether comments should be ignored and treated like whitespace (true) or yield a parse error (true); (optional, false by default)
Returns
Whether the input read from i is valid JSON.

@complexity Linear in the length of the input. The parser is a predictive LL(1) parser.

Note
A UTF-8 byte order mark is silently ignored.

@liveexample{The example below demonstrates the accept() function reading from a string.,accept__string}

Definition at line 24339 of file json.hpp.

References nlohmann::detail::input_adapter(), and parser().

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◆ accept() [3/3]

template<typename IteratorType >
static bool nlohmann::basic_json::accept ( IteratorType  first,
IteratorType  last,
const bool  ignore_comments = false 
)
inlinestatic

Definition at line 24346 of file json.hpp.

References nlohmann::detail::input_adapter(), and parser().

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◆ array()

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::array ( initializer_list_t  init = {})
inlinestatic

explicitly create an array from an initializer list

Creates a JSON array value from a given initializer list. That is, given a list of values a, b, c, creates the JSON value [a, b, c]. If the initializer list is empty, the empty array [] is created.

Note
This function is only needed to express two edge cases that cannot be realized with the initializer list constructor (basic_json(initializer_list_t, bool, value_t)). These cases are:
  1. creating an array whose elements are all pairs whose first element is a string – in this case, the initializer list constructor would create an object, taking the first elements as keys
  2. creating an empty array – passing the empty initializer list to the initializer list constructor yields an empty object
Parameters
[in]initinitializer list with JSON values to create an array from (optional)
Returns
JSON array value

@complexity Linear in the size of init.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

@liveexample{The following code shows an example for the array function.,array}

See also
see basic_json(initializer_list_t, bool, value_t)create a JSON value from an initializer list
see object(initializer_list_t)create a JSON object value from an initializer list
Since
version 1.0.0

Definition at line 19282 of file json.hpp.

◆ assert_invariant()

void nlohmann::basic_json::assert_invariant ( bool  check_parents = true) const
inlineprivatenoexcept

checks the class invariants

This function asserts the class invariants. It needs to be called at the end of every constructor to make sure that created objects respect the invariant. Furthermore, it has to be called each time the type of a JSON value is changed, because the invariant expresses a relationship between m_type and m_value.

Furthermore, the parent relation is checked for arrays and objects: If check_parents true and the value is an array or object, then the container's elements must have the current value as parent.

Parameters
[in]check_parentswhether the parent relation should be checked. The value is true by default and should only be set to false during destruction of objects when the invariant does not need to hold.

Definition at line 18634 of file json.hpp.

References nlohmann::detail::array, begin(), nlohmann::detail::binary, end(), is_structured(), JSON_ASSERT, JSON_CATCH, JSON_TRY, m_value, nlohmann::detail::object, and nlohmann::detail::string.

Referenced by basic_json(), emplace(), emplace_back(), erase(), operator=(), operator[](), push_back(), swap(), update(), and ~basic_json().

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◆ at() [1/6]

reference nlohmann::basic_json::at ( const json_pointer ptr)
inline

access specified element via JSON Pointer

Returns a reference to the element at with specified JSON pointer ptr, with bounds checking.

Parameters
[in]ptrJSON pointer to the desired element
Returns
reference to the element pointed to by ptr
Exceptions
parse_error.106if an array index in the passed JSON pointer ptr begins with '0'. See example below.
parse_error.109if an array index in the passed JSON pointer ptr is not a number. See example below.
out_of_range.401if an array index in the passed JSON pointer ptr is out of range. See example below.
out_of_range.402if the array index '-' is used in the passed JSON pointer ptr. As at provides checked access (and no elements are implicitly inserted), the index '-' is always invalid. See example below.
out_of_range.403if the JSON pointer describes a key of an object which cannot be found. See example below.
out_of_range.404if the JSON pointer ptr can not be resolved. See example below.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Constant.

Since
version 2.0.0

@liveexample{The behavior is shown in the example.,at_json_pointer}

Definition at line 25623 of file json.hpp.

◆ at() [2/6]

const_reference nlohmann::basic_json::at ( const json_pointer ptr) const
inline

access specified element via JSON Pointer

Returns a const reference to the element at with specified JSON pointer ptr, with bounds checking.

Parameters
[in]ptrJSON pointer to the desired element
Returns
reference to the element pointed to by ptr
Exceptions
parse_error.106if an array index in the passed JSON pointer ptr begins with '0'. See example below.
parse_error.109if an array index in the passed JSON pointer ptr is not a number. See example below.
out_of_range.401if an array index in the passed JSON pointer ptr is out of range. See example below.
out_of_range.402if the array index '-' is used in the passed JSON pointer ptr. As at provides checked access (and no elements are implicitly inserted), the index '-' is always invalid. See example below.
out_of_range.403if the JSON pointer describes a key of an object which cannot be found. See example below.
out_of_range.404if the JSON pointer ptr can not be resolved. See example below.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Constant.

Since
version 2.0.0

@liveexample{The behavior is shown in the example.,at_json_pointer_const}

Definition at line 25666 of file json.hpp.

◆ at() [3/6]

reference nlohmann::basic_json::at ( const typename object_t::key_type &  key)
inline

access specified object element with bounds checking

Returns a reference to the element at with specified key key, with bounds checking.

Parameters
[in]keykey of the element to access
Returns
reference to the element at key key
Exceptions
type_error.304if the JSON value is not an object; in this case, calling at with a key makes no sense. See example below.
out_of_range.403if the key key is is not stored in the object; that is, find(key) == end(). See example below.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Logarithmic in the size of the container.

See also
see operator[](const typename object_t::key_type&) for unchecked access by reference
see value() for access by value with a default value
Since
version 1.0.0

@liveexample{The example below shows how object elements can be read and written using at(). It also demonstrates the different exceptions that can be thrown.,at__object_t_key_type}

Definition at line 20950 of file json.hpp.

References nlohmann::detail::type_error::create(), nlohmann::detail::out_of_range::create(), is_object(), JSON_CATCH, JSON_HEDLEY_LIKELY, JSON_THROW, JSON_TRY, m_value, set_parent(), and type_name().

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◆ at() [4/6]

const_reference nlohmann::basic_json::at ( const typename object_t::key_type &  key) const
inline

access specified object element with bounds checking

Returns a const reference to the element at with specified key key, with bounds checking.

Parameters
[in]keykey of the element to access
Returns
const reference to the element at key key
Exceptions
type_error.304if the JSON value is not an object; in this case, calling at with a key makes no sense. See example below.
out_of_range.403if the key key is is not stored in the object; that is, find(key) == end(). See example below.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Logarithmic in the size of the container.

See also
see operator[](const typename object_t::key_type&) for unchecked access by reference
see value() for access by value with a default value
Since
version 1.0.0

@liveexample{The example below shows how object elements can be read using at(). It also demonstrates the different exceptions that can be thrown., at__object_t_key_type_const}

Definition at line 21001 of file json.hpp.

References nlohmann::detail::type_error::create(), nlohmann::detail::out_of_range::create(), is_object(), JSON_CATCH, JSON_HEDLEY_LIKELY, JSON_THROW, JSON_TRY, m_value, and type_name().

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◆ at() [5/6]

reference nlohmann::basic_json::at ( size_type  idx)
inline

access specified array element with bounds checking

Returns a reference to the element at specified location idx, with bounds checking.

Parameters
[in]idxindex of the element to access
Returns
reference to the element at index idx
Exceptions
type_error.304if the JSON value is not an array; in this case, calling at with an index makes no sense. See example below.
out_of_range.401if the index idx is out of range of the array; that is, idx >= size(). See example below.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Constant.

Since
version 1.0.0

@liveexample{The example below shows how array elements can be read and written using at(). It also demonstrates the different exceptions that can be thrown.,at__size_type}

Definition at line 20852 of file json.hpp.

References nlohmann::detail::type_error::create(), nlohmann::detail::out_of_range::create(), is_array(), JSON_CATCH, JSON_HEDLEY_LIKELY, JSON_THROW, JSON_TRY, m_value, set_parent(), nlohmann::to_string(), and type_name().

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◆ at() [6/6]

const_reference nlohmann::basic_json::at ( size_type  idx) const
inline

access specified array element with bounds checking

Returns a const reference to the element at specified location idx, with bounds checking.

Parameters
[in]idxindex of the element to access
Returns
const reference to the element at index idx
Exceptions
type_error.304if the JSON value is not an array; in this case, calling at with an index makes no sense. See example below.
out_of_range.401if the index idx is out of range of the array; that is, idx >= size(). See example below.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Constant.

Since
version 1.0.0

@liveexample{The example below shows how array elements can be read using at(). It also demonstrates the different exceptions that can be thrown., at__size_type_const}

Definition at line 20899 of file json.hpp.

References nlohmann::detail::type_error::create(), nlohmann::detail::out_of_range::create(), is_array(), JSON_CATCH, JSON_HEDLEY_LIKELY, JSON_THROW, JSON_TRY, m_value, nlohmann::to_string(), and type_name().

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◆ back() [1/2]

reference nlohmann::basic_json::back ( )
inline

access the last element

Returns a reference to the last element in the container. For a JSON container c, the expression c.back() is equivalent to

auto tmp = c.end();
--tmp;
return *tmp;
Returns
In case of a structured type (array or object), a reference to the last element is returned. In case of number, string, boolean, or binary values, a reference to the value is returned.

@complexity Constant.

Precondition
The JSON value must not be null (would throw std::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
Postcondition
The JSON value remains unchanged.
Exceptions
invalid_iterator.214when called on a null value. See example below.

@liveexample{The following code shows an example for back().,back}

See also
see front() – access the first element
Since
version 1.0.0

Definition at line 21515 of file json.hpp.

References end(), and Ice::tmp.

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◆ back() [2/2]

const_reference nlohmann::basic_json::back ( ) const
inline

access the last element

Returns a reference to the last element in the container. For a JSON container c, the expression c.back() is equivalent to

auto tmp = c.end();
--tmp;
return *tmp;
Returns
In case of a structured type (array or object), a reference to the last element is returned. In case of number, string, boolean, or binary values, a reference to the value is returned.

@complexity Constant.

Precondition
The JSON value must not be null (would throw std::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
Postcondition
The JSON value remains unchanged.
Exceptions
invalid_iterator.214when called on a null value. See example below.

@liveexample{The following code shows an example for back().,back}

See also
see front() – access the first element
Since
version 1.0.0

Definition at line 21525 of file json.hpp.

References cend(), and Ice::tmp.

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◆ begin() [1/2]

const_iterator nlohmann::basic_json::begin ( ) const
inlinenoexcept

returns a const iterator to the first element

Returns a const iterator to the first element.

Illustration from cppreference.com
Returns
const iterator to the first element

@complexity Constant.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is constant.
  • Has the semantics of const_cast<const basic_json&>(*this).begin().

@liveexample{The following code shows an example for cbegin().,cbegin}

See also
see begin() – returns an iterator to the beginning
see end() – returns an iterator to the end
see cend() – returns a const iterator to the end
Since
version 1.0.0

Definition at line 22046 of file json.hpp.

References cbegin().

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◆ begin() [2/2]

iterator nlohmann::basic_json::begin ( )
inlinenoexcept

returns an iterator to the first element

Returns an iterator to the first element.

Illustration from cppreference.com
Returns
iterator to the first element

@complexity Constant.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is constant.

@liveexample{The following code shows an example for begin().,begin}

See also
see cbegin() – returns a const iterator to the beginning
see end() – returns an iterator to the end
see cend() – returns a const iterator to the end
Since
version 1.0.0

Definition at line 22036 of file json.hpp.

References rotate-tower::result.

Referenced by assert_invariant(), emplace(), front(), operator[](), and rend().

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◆ binary() [1/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::binary ( const typename binary_t::container_type init)
inlinestatic

explicitly create a binary array (without subtype)

Creates a JSON binary array value from a given binary container. Binary values are part of various binary formats, such as CBOR, MessagePack, and BSON. This constructor is used to create a value for serialization to those formats.

Note
Note, this function exists because of the difficulty in correctly specifying the correct template overload in the standard value ctor, as both JSON arrays and JSON binary arrays are backed with some form of a std::vector. Because JSON binary arrays are a non-standard extension it was decided that it would be best to prevent automatic initialization of a binary array type, for backwards compatibility and so it does not happen on accident.
Parameters
[in]initcontainer containing bytes to use as binary type
Returns
JSON binary array value

@complexity Linear in the size of init.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

Since
version 3.8.0

Definition at line 19179 of file json.hpp.

References basic_json(), nlohmann::detail::binary, init(), and altar_valkyrie::res.

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◆ binary() [2/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::binary ( const typename binary_t::container_type init,
typename binary_t::subtype_type  subtype 
)
inlinestatic

explicitly create a binary array (with subtype)

Creates a JSON binary array value from a given binary container. Binary values are part of various binary formats, such as CBOR, MessagePack, and BSON. This constructor is used to create a value for serialization to those formats.

Note
Note, this function exists because of the difficulty in correctly specifying the correct template overload in the standard value ctor, as both JSON arrays and JSON binary arrays are backed with some form of a std::vector. Because JSON binary arrays are a non-standard extension it was decided that it would be best to prevent automatic initialization of a binary array type, for backwards compatibility and so it does not happen on accident.
Parameters
[in]initcontainer containing bytes to use as binary type
[in]subtypesubtype to use in MessagePack and BSON
Returns
JSON binary array value

@complexity Linear in the size of init.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

Since
version 3.8.0

Definition at line 19216 of file json.hpp.

References basic_json(), nlohmann::detail::binary, init(), and altar_valkyrie::res.

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◆ binary() [3/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::binary ( typename binary_t::container_type &&  init)
inlinestatic

explicitly create a binary array (without subtype)

Creates a JSON binary array value from a given binary container. Binary values are part of various binary formats, such as CBOR, MessagePack, and BSON. This constructor is used to create a value for serialization to those formats.

Note
Note, this function exists because of the difficulty in correctly specifying the correct template overload in the standard value ctor, as both JSON arrays and JSON binary arrays are backed with some form of a std::vector. Because JSON binary arrays are a non-standard extension it was decided that it would be best to prevent automatic initialization of a binary array type, for backwards compatibility and so it does not happen on accident.
Parameters
[in]initcontainer containing bytes to use as binary type
Returns
JSON binary array value

@complexity Linear in the size of init.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

Since
version 3.8.0

Definition at line 19226 of file json.hpp.

References basic_json(), nlohmann::detail::binary, init(), and altar_valkyrie::res.

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◆ binary() [4/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::binary ( typename binary_t::container_type &&  init,
typename binary_t::subtype_type  subtype 
)
inlinestatic

explicitly create a binary array (with subtype)

Creates a JSON binary array value from a given binary container. Binary values are part of various binary formats, such as CBOR, MessagePack, and BSON. This constructor is used to create a value for serialization to those formats.

Note
Note, this function exists because of the difficulty in correctly specifying the correct template overload in the standard value ctor, as both JSON arrays and JSON binary arrays are backed with some form of a std::vector. Because JSON binary arrays are a non-standard extension it was decided that it would be best to prevent automatic initialization of a binary array type, for backwards compatibility and so it does not happen on accident.
Parameters
[in]initcontainer containing bytes to use as binary type
[in]subtypesubtype to use in MessagePack and BSON
Returns
JSON binary array value

@complexity Linear in the size of init.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes to any JSON value.

Since
version 3.8.0

Definition at line 19236 of file json.hpp.

References basic_json(), nlohmann::detail::binary, init(), and altar_valkyrie::res.

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◆ cbegin()

const_iterator nlohmann::basic_json::cbegin ( ) const
inlinenoexcept

returns a const iterator to the first element

Returns a const iterator to the first element.

Illustration from cppreference.com
Returns
const iterator to the first element

@complexity Constant.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is constant.
  • Has the semantics of const_cast<const basic_json&>(*this).begin().

@liveexample{The following code shows an example for cbegin().,cbegin}

See also
see begin() – returns an iterator to the beginning
see end() – returns an iterator to the end
see cend() – returns a const iterator to the end
Since
version 1.0.0

Definition at line 22076 of file json.hpp.

References rotate-tower::result.

Referenced by begin(), crend(), front(), and update().

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◆ cend()

const_iterator nlohmann::basic_json::cend ( ) const
inlinenoexcept

returns a const iterator to one past the last element

Returns a const iterator to one past the last element.

Illustration from cppreference.com
Returns
const iterator one past the last element

@complexity Constant.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is constant.
  • Has the semantics of const_cast<const basic_json&>(*this).end().

@liveexample{The following code shows an example for cend().,cend}

See also
see end() – returns an iterator to the end
see begin() – returns an iterator to the beginning
see cbegin() – returns a const iterator to the beginning
Since
version 1.0.0

Definition at line 22147 of file json.hpp.

References rotate-tower::result.

Referenced by back(), crbegin(), end(), find(), and update().

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◆ clear()

void nlohmann::basic_json::clear ( )
inlinenoexcept

clears the contents

Clears the content of a JSON value and resets it to the default value as if basic_json(value_t) would have been called with the current value type from type():

Value type initial value
null null
boolean false
string ""
number 0
binary An empty byte vector
object {}
array []
Postcondition
Has the same effect as calling
*this = basic_json(type());

@liveexample{The example below shows the effect of clear() to different JSON types.,clear}

@complexity Linear in the size of the JSON value.

@iterators All iterators, pointers and references related to this container are invalidated.

@exceptionsafety No-throw guarantee: this function never throws exceptions.

See also
see basic_json(value_t) – constructor that creates an object with the same value than calling clear()
Since
version 1.0.0

Definition at line 22728 of file json.hpp.

References nlohmann::detail::array, nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::discarded, m_value, nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, and nlohmann::detail::string.

◆ contains() [1/2]

bool nlohmann::basic_json::contains ( const json_pointer ptr) const
inline

check the existence of an element in a JSON object given a JSON pointer

Check whether the given JSON pointer ptr can be resolved in the current JSON value.

Note
This method can be executed on any JSON value type.
Parameters
[in]ptrJSON pointer to check its existence.
Returns
true if the JSON pointer can be resolved to a stored value, false otherwise.
Postcondition
If j.contains(ptr) returns true, it is safe to call j[ptr].
Exceptions
parse_error.106if an array index begins with '0'
parse_error.109if an array index was not a number

@complexity Logarithmic in the size of the JSON object.

@liveexample{The following code shows an example for contains().,contains_json_pointer}

See also
see contains(KeyT &&) const – checks the existence of a key
Since
version 3.7.0

Definition at line 21997 of file json.hpp.

◆ contains() [2/2]

template<typename KeyT , typename std::enable_if< !std::is_same< typename std::decay< KeyT >::type, json_pointer >::value, int >::type = 0>
bool nlohmann::basic_json::contains ( KeyT &&  key) const
inline

check the existence of an element in a JSON object

Check whether an element exists in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, false is returned.

Note
This method always returns false when executed on a JSON type that is not an object.
Parameters
[in]keykey value to check its existence.
Returns
true if an element with specified key exists. If no such element with such key is found or the JSON value is not an object, false is returned.

@complexity Logarithmic in the size of the JSON object.

@liveexample{The following code shows an example for contains().,contains}

See also
see find(KeyT&&) – returns an iterator to an object element
see contains(const json_pointer&) const – checks the existence for a JSON pointer
Since
version 3.6.0

Definition at line 21966 of file json.hpp.

References is_object(), and m_value.

Referenced by inja::Renderer::visit().

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◆ count()

template<typename KeyT >
size_type nlohmann::basic_json::count ( KeyT &&  key) const
inline

returns the number of occurrences of a key in a JSON object

Returns the number of elements with key key. If ObjectType is the default std::map type, the return value will always be 0 (key was not found) or 1 (key was found).

Note
This method always returns 0 when executed on a JSON type that is not an object.
Parameters
[in]keykey value of the element to count
Returns
Number of elements with key key. If the JSON value is not an object, the return value will be 0.

@complexity Logarithmic in the size of the JSON object.

@liveexample{The example shows how count() is used.,count}

Since
version 1.0.0

Definition at line 21933 of file json.hpp.

References is_object(), and m_value.

Referenced by set_parents().

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◆ crbegin()

const_reverse_iterator nlohmann::basic_json::crbegin ( ) const
inlinenoexcept

returns a const reverse iterator to the last element

Returns a const iterator to the reverse-beginning; that is, the last element.

Illustration from cppreference.com

@complexity Constant.

@requirement This function helps basic_json satisfying the ReversibleContainer requirements:

  • The complexity is constant.
  • Has the semantics of const_cast<const basic_json&>(*this).rbegin().

@liveexample{The following code shows an example for crbegin().,crbegin}

See also
see rbegin() – returns a reverse iterator to the beginning
see rend() – returns a reverse iterator to the end
see crend() – returns a const reverse iterator to the end
Since
version 1.0.0

Definition at line 22251 of file json.hpp.

References cend().

Referenced by rbegin().

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◆ create()

template<typename T , typename... Args>
static JSON_HEDLEY_RETURNS_NON_NULL T* nlohmann::basic_json::create ( Args &&...  args)
inlinestaticprivate

helper for exception-safe object creation

Definition at line 18310 of file json.hpp.

References make_face_from_files::args, JSON_ASSERT, and altar_valkyrie::obj.

◆ crend()

const_reverse_iterator nlohmann::basic_json::crend ( ) const
inlinenoexcept

returns a const reverse iterator to one before the first

Returns a const reverse iterator to the reverse-end; that is, one before the first element.

Illustration from cppreference.com

@complexity Constant.

@requirement This function helps basic_json satisfying the ReversibleContainer requirements:

  • The complexity is constant.
  • Has the semantics of const_cast<const basic_json&>(*this).rend().

@liveexample{The following code shows an example for crend().,crend}

See also
see rend() – returns a reverse iterator to the end
see rbegin() – returns a reverse iterator to the beginning
see crbegin() – returns a const reverse iterator to the beginning
Since
version 1.0.0

Definition at line 22280 of file json.hpp.

References cbegin().

Referenced by rend().

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◆ destroy()

◆ diff()

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::diff ( const basic_json source,
const basic_json target,
const std::string &  path = "" 
)
inlinestatic

creates a diff as a JSON patch

Creates a JSON Patch so that value source can be changed into the value target by calling patch function.

Invariant
For two JSON values source and target, the following code yields always true:
source.patch(diff(source, target)) == target;
Note
Currently, only remove, add, and replace operations are generated.
Parameters
[in]sourceJSON value to compare from
[in]targetJSON value to compare against
[in]pathhelper value to create JSON pointers
Returns
a JSON patch to convert the source to target

@complexity Linear in the lengths of source and target.

@liveexample{The following code shows how a JSON patch is created as a diff for two JSON values.,diff}

See also
see patch – apply a JSON patch
see merge_patch – apply a JSON Merge Patch
RFC 6902 (JSON Patch)
Since
version 2.0.0

Definition at line 26097 of file json.hpp.

References nlohmann::detail::array, nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::discarded, nlohmann::detail::escape(), nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, object(), python_init::path, rotate-tower::result, nlohmann::detail::string, and nlohmann::to_string().

Referenced by fill_json().

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◆ dump()

string_t nlohmann::basic_json::dump ( const int  indent = -1,
const char  indent_char = ' ',
const bool  ensure_ascii = false,
const error_handler_t  error_handler = error_handler_t::strict 
) const
inline

serialization

Serialization function for JSON values. The function tries to mimic Python's json.dumps() function, and currently supports its indent and ensure_ascii parameters.

Parameters
[in]indentIf indent is nonnegative, then array elements and object members will be pretty-printed with that indent level. An indent level of 0 will only insert newlines. -1 (the default) selects the most compact representation.
[in]indent_charThe character to use for indentation if indent is greater than 0. The default is (space).
[in]ensure_asciiIf ensure_ascii is true, all non-ASCII characters in the output are escaped with \uXXXX sequences, and the result consists of ASCII characters only.
[in]error_handlerhow to react on decoding errors; there are three possible values: strict (throws and exception in case a decoding error occurs; default), replace (replace invalid UTF-8 sequences with U+FFFD), and ignore (ignore invalid UTF-8 sequences during serialization; all bytes are copied to the output unchanged).
Returns
string containing the serialization of the JSON value
Exceptions
type_error.316if a string stored inside the JSON value is not UTF-8 encoded and error_handler is set to strict
Note
Binary values are serialized as object containing two keys:
  • "bytes": an array of bytes as integers
  • "subtype": the subtype as integer or "null" if the binary has no subtype

@complexity Linear.

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@liveexample{The following example shows the effect of different indent\, indent_char\, and ensure_ascii parameters to the result of the serialization.,dump}

See also
https://docs.python.org/2/library/json.html#json.dump
Since
version 1.0.0; indentation character indent_char, option ensure_ascii and exceptions added in version 3.0.0; error handlers added in version 3.4.0; serialization of binary values added in version 3.8.0.

Definition at line 19784 of file json.hpp.

References rotate-tower::result.

◆ emplace()

template<class... Args>
std::pair<iterator, bool> nlohmann::basic_json::emplace ( Args &&...  args)
inline

add an object to an object if key does not exist

Inserts a new element into a JSON object constructed in-place with the given args if there is no element with the key in the container. If the function is called on a JSON null value, an empty object is created before appending the value created from args.

Parameters
[in]argsarguments to forward to a constructor of basic_json
Template Parameters
Argscompatible types to create a basic_json object
Returns
a pair consisting of an iterator to the inserted element, or the already-existing element if no insertion happened, and a bool denoting whether the insertion took place.
Exceptions
type_error.311when called on a type other than JSON object or null; example: "cannot use emplace() with number"

@complexity Logarithmic in the size of the container, O(log(size())).

@liveexample{The example shows how emplace() can be used to add elements to a JSON object. Note how the null value was silently converted to a JSON object. Further note how no value is added if there was already one value stored with the same key.,emplace}

Since
version 2.0.8

Definition at line 23050 of file json.hpp.

References make_face_from_files::args, assert_invariant(), begin(), nlohmann::detail::type_error::create(), is_null(), is_object(), JSON_HEDLEY_UNLIKELY, JSON_THROW, m_value, nlohmann::detail::object, altar_valkyrie::res, set_parent(), and type_name().

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◆ emplace_back()

template<class... Args>
reference nlohmann::basic_json::emplace_back ( Args &&...  args)
inline

add an object to an array

Creates a JSON value from the passed parameters args to the end of the JSON value. If the function is called on a JSON null value, an empty array is created before appending the value created from args.

Parameters
[in]argsarguments to forward to a constructor of basic_json
Template Parameters
Argscompatible types to create a basic_json object
Returns
reference to the inserted element
Exceptions
type_error.311when called on a type other than JSON array or null; example: "cannot use emplace_back() with number"

@complexity Amortized constant.

@liveexample{The example shows how push_back() can be used to add elements to a JSON array. Note how the null value was silently converted to a JSON array.,emplace_back}

Since
version 2.0.8, returns reference since 3.7.0

Definition at line 23000 of file json.hpp.

References make_face_from_files::args, nlohmann::detail::array, assert_invariant(), nlohmann::detail::type_error::create(), is_array(), is_null(), JSON_HEDLEY_UNLIKELY, JSON_THROW, m_value, set_parent(), and type_name().

Referenced by inja::Renderer::render_to().

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◆ empty()

bool nlohmann::basic_json::empty ( ) const
inlinenoexcept

checks whether the container is empty.

Checks if a JSON value has no elements (i.e. whether its size is 0).

Returns
The return value depends on the different types and is defined as follows:
Value type return value
null true
boolean false
string false
number false
binary false
object result of function object_t::empty()
array result of function array_t::empty()

@liveexample{The following code uses empty() to check if a JSON object contains any elements.,empty}

@complexity Constant, as long as array_t and object_t satisfy the Container concept; that is, their empty() functions have constant complexity.

@iterators No changes.

@exceptionsafety No-throw guarantee: this function never throws exceptions.

Note
This function does not return whether a string stored as JSON value is empty - it returns whether the JSON container itself is empty which is false in the case of a string.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is constant.
  • Has the semantics of begin() == end().
See also
see size() – returns the number of elements
Since
version 1.0.0

Definition at line 22491 of file json.hpp.

References nlohmann::detail::array, nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::discarded, m_value, nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, and nlohmann::detail::string.

Referenced by inja::Renderer::visit().

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◆ end() [1/2]

const_iterator nlohmann::basic_json::end ( ) const
inlinenoexcept

returns a const iterator to one past the last element

Returns a const iterator to one past the last element.

Illustration from cppreference.com
Returns
const iterator one past the last element

@complexity Constant.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is constant.
  • Has the semantics of const_cast<const basic_json&>(*this).end().

@liveexample{The following code shows an example for cend().,cend}

See also
see end() – returns an iterator to the end
see begin() – returns an iterator to the beginning
see cbegin() – returns a const iterator to the beginning
Since
version 1.0.0

Definition at line 22117 of file json.hpp.

References cend().

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◆ end() [2/2]

iterator nlohmann::basic_json::end ( )
inlinenoexcept

returns an iterator to one past the last element

Returns an iterator to one past the last element.

Illustration from cppreference.com
Returns
iterator one past the last element

@complexity Constant.

@requirement This function helps basic_json satisfying the Container requirements:

  • The complexity is constant.

@liveexample{The following code shows an example for end().,end}

See also
see cend() – returns a const iterator to the end
see begin() – returns an iterator to the beginning
see cbegin() – returns a const iterator to the beginning
Since
version 1.0.0

Definition at line 22107 of file json.hpp.

References rotate-tower::result.

Referenced by assert_invariant(), back(), erase(), find(), rbegin(), and value().

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◆ erase() [1/4]

void nlohmann::basic_json::erase ( const size_type  idx)
inline

remove element from a JSON array given an index

Removes element from a JSON array at the index idx.

Parameters
[in]idxindex of the element to remove
Exceptions
type_error.307when called on a type other than JSON object; example: "cannot use erase() with null"
out_of_range.401when idx >= size(); example: "array index 17 is out of range"

@complexity Linear in distance between idx and the end of the container.

@liveexample{The example shows the effect of erase().,erase__size_type}

See also
see erase(IteratorType) – removes the element at a given position
see erase(IteratorType, IteratorType) – removes the elements in the given range
see erase(const typename object_t::key_type&) – removes the element from an object at the given key
Since
version 1.0.0

Definition at line 21829 of file json.hpp.

References nlohmann::detail::type_error::create(), nlohmann::detail::out_of_range::create(), is_array(), JSON_HEDLEY_LIKELY, JSON_HEDLEY_UNLIKELY, JSON_THROW, m_value, size(), nlohmann::to_string(), and type_name().

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◆ erase() [2/4]

size_type nlohmann::basic_json::erase ( const typename object_t::key_type &  key)
inline

remove element from a JSON object given a key

Removes elements from a JSON object with the key value key.

Parameters
[in]keyvalue of the elements to remove
Returns
Number of elements removed. If ObjectType is the default std::map type, the return value will always be 0 (key was not found) or 1 (key was found).
Postcondition
References and iterators to the erased elements are invalidated. Other references and iterators are not affected.
Exceptions
type_error.307when called on a type other than JSON object; example: "cannot use erase() with null"

@complexity log(size()) + count(key)

@liveexample{The example shows the effect of erase().,erase__key_type}

See also
see erase(IteratorType) – removes the element at a given position
see erase(IteratorType, IteratorType) – removes the elements in the given range
see erase(const size_type) – removes the element from an array at the given index
Since
version 1.0.0

Definition at line 21794 of file json.hpp.

References nlohmann::detail::type_error::create(), is_object(), JSON_HEDLEY_LIKELY, JSON_THROW, m_value, and type_name().

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◆ erase() [3/4]

template<class IteratorType , typename std::enable_if< std::is_same< IteratorType, typename basic_json_t::iterator >::value||std::is_same< IteratorType, typename basic_json_t::const_iterator >::value, int >::type = 0>
IteratorType nlohmann::basic_json::erase ( IteratorType  first,
IteratorType  last 
)
inline

remove elements given an iterator range

Removes the element specified by the range [first; last). The iterator first does not need to be dereferenceable if first == last: erasing an empty range is a no-op.

If called on a primitive type other than null, the resulting JSON value will be null.

Parameters
[in]firstiterator to the beginning of the range to remove
[in]lastiterator past the end of the range to remove
Returns
Iterator following the last removed element. If the iterator second refers to the last element, the end() iterator is returned.
Template Parameters
IteratorTypean iterator or const_iterator
Postcondition
Invalidates iterators and references at or after the point of the erase, including the end() iterator.
Exceptions
type_error.307if called on a null value; example: "cannot use erase() with null"
invalid_iterator.203if called on iterators which does not belong to the current JSON value; example: "iterators do not fit current value"
invalid_iterator.204if called on a primitive type with invalid iterators (i.e., if first != begin() and last != end()); example: "iterators out of range"

@complexity The complexity depends on the type:

  • objects: log(size()) + std::distance(first, last)
  • arrays: linear in the distance between first and last, plus linear in the distance between last and end of the container
  • strings and binary: linear in the length of the member
  • other types: constant

@liveexample{The example shows the result of erase() for different JSON types.,erase__IteratorType_IteratorType}

See also
see erase(IteratorType) – removes the element at a given position
see erase(const typename object_t::key_type&) – removes the element from an object at the given key
see erase(const size_type) – removes the element from an array at the given index
Since
version 1.0.0

Definition at line 21697 of file json.hpp.

References nlohmann::detail::array, assert_invariant(), nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::invalid_iterator::create(), nlohmann::detail::type_error::create(), destroy(), nlohmann::detail::discarded, end(), is_binary(), is_string(), JSON_HEDLEY_LIKELY, JSON_HEDLEY_UNLIKELY, JSON_THROW, m_value, nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, rotate-tower::result, nlohmann::detail::string, and type_name().

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◆ erase() [4/4]

template<class IteratorType , typename std::enable_if< std::is_same< IteratorType, typename basic_json_t::iterator >::value||std::is_same< IteratorType, typename basic_json_t::const_iterator >::value, int >::type = 0>
IteratorType nlohmann::basic_json::erase ( IteratorType  pos)
inline

remove element given an iterator

Removes the element specified by iterator pos. The iterator pos must be valid and dereferenceable. Thus the end() iterator (which is valid, but is not dereferenceable) cannot be used as a value for pos.

If called on a primitive type other than null, the resulting JSON value will be null.

Parameters
[in]positerator to the element to remove
Returns
Iterator following the last removed element. If the iterator pos refers to the last element, the end() iterator is returned.
Template Parameters
IteratorTypean iterator or const_iterator
Postcondition
Invalidates iterators and references at or after the point of the erase, including the end() iterator.
Exceptions
type_error.307if called on a null value; example: "cannot use erase() with null"
invalid_iterator.202if called on an iterator which does not belong to the current JSON value; example: "iterator does not fit current value"
invalid_iterator.205if called on a primitive type with invalid iterator (i.e., any iterator which is not begin()); example: "iterator out of range"

@complexity The complexity depends on the type:

  • objects: amortized constant
  • arrays: linear in distance between pos and the end of the container
  • strings and binary: linear in the length of the member
  • other types: constant

@liveexample{The example shows the result of erase() for different JSON types.,erase__IteratorType}

See also
see erase(IteratorType, IteratorType) – removes the elements in the given range
see erase(const typename object_t::key_type&) – removes the element from an object at the given key
see erase(const size_type) – removes the element from an array at the given index
Since
version 1.0.0

Definition at line 21582 of file json.hpp.

References nlohmann::detail::array, assert_invariant(), nlohmann::detail::binary, nlohmann::detail::boolean, nlohmann::detail::invalid_iterator::create(), nlohmann::detail::type_error::create(), destroy(), nlohmann::detail::discarded, end(), is_binary(), is_string(), JSON_HEDLEY_UNLIKELY, JSON_THROW, m_value, nlohmann::detail::null, nlohmann::detail::number_float, nlohmann::detail::number_integer, nlohmann::detail::number_unsigned, nlohmann::detail::object, rotate-tower::result, nlohmann::detail::string, and type_name().

Referenced by main(), and merge_patch().

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◆ find() [1/2]

template<typename KeyT >
iterator nlohmann::basic_json::find ( KeyT &&  key)
inline

find an element in a JSON object

Finds an element in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, end() is returned.

Note
This method always returns end() when executed on a JSON type that is not an object.
Parameters
[in]keykey value of the element to search for.
Returns
Iterator to an element with key equivalent to key. If no such element is found or the JSON value is not an object, past-the-end (see end()) iterator is returned.

@complexity Logarithmic in the size of the JSON object.

@liveexample{The example shows how find() is used.,find__key_type}

See also
see contains(KeyT&&) const – checks whether a key exists
Since
version 1.0.0

Definition at line 21882 of file json.hpp.

References end(), is_object(), m_value, and rotate-tower::result.

Referenced by value().

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◆ find() [2/2]

template<typename KeyT >
const_iterator nlohmann::basic_json::find ( KeyT &&  key) const
inline

find an element in a JSON object

find an element in a JSON object Finds an element in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, end() is returned.

Note
This method always returns end() when executed on a JSON type that is not an object.
Parameters
[in]keykey value of the element to search for.
Returns
Iterator to an element with key equivalent to key. If no such element is found or the JSON value is not an object, past-the-end (see end()) iterator is returned.

@complexity Logarithmic in the size of the JSON object.

@liveexample{The example shows how find() is used.,find__key_type}

See also
see contains(KeyT&&) const – checks whether a key exists
Since
version 1.0.0

Definition at line 21899 of file json.hpp.

References cend(), is_object(), m_value, and rotate-tower::result.

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◆ flatten()

basic_json nlohmann::basic_json::flatten ( ) const
inline

return flattened JSON value

The function creates a JSON object whose keys are JSON pointers (see RFC 6901) and whose values are all primitive. The original JSON value can be restored using the unflatten() function.

Returns
an object that maps JSON pointers to primitive values
Note
Empty objects and arrays are flattened to null and will not be reconstructed correctly by the unflatten() function.

@complexity Linear in the size the JSON value.

@liveexample{The following code shows how a JSON object is flattened to an object whose keys consist of JSON pointers.,flatten}

See also
see unflatten() for the reverse function
Since
version 2.0.0

Definition at line 25693 of file json.hpp.

References nlohmann::json_pointer< BasicJsonType >::flatten(), nlohmann::detail::object, and rotate-tower::result.

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◆ from_bson() [1/4]

template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_bson ( const T *  ptr,
std::size_t  len,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

Definition at line 25490 of file json.hpp.

References from_bson().

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◆ from_bson() [2/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_bson ( detail::span_input_adapter &&  i,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

◆ from_bson() [3/4]

template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_bson ( InputType &&  i,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

Create a JSON value from an input in BSON format.

Deserializes a given input i to a JSON value using the BSON (Binary JSON) serialization format.

The library maps BSON record types to JSON value types as follows:

BSON type BSON marker byte JSON value type
double 0x01 number_float
string 0x02 string
document 0x03 object
array 0x04 array
binary 0x05 binary
undefined 0x06 still unsupported
ObjectId 0x07 still unsupported
boolean 0x08 boolean
UTC Date-Time 0x09 still unsupported
null 0x0A null
Regular Expr. 0x0B still unsupported
DB Pointer 0x0C still unsupported
JavaScript Code 0x0D still unsupported
Symbol 0x0E still unsupported
JavaScript Code 0x0F still unsupported
int32 0x10 number_integer
Timestamp 0x11 still unsupported
128-bit decimal float 0x13 still unsupported
Max Key 0x7F still unsupported
Min Key 0xFF still unsupported
Warning
The mapping is incomplete. The unsupported mappings are indicated in the table above.
Parameters
[in]ian input in BSON format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.114if an unsupported BSON record type is encountered

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in BSON format to a JSON value.,from_bson}

See also
http://bsonspec.org/spec.html
see to_bson(const basic_json&) for the analogous serialization
see from_cbor(InputType&&, const bool, const bool, const cbor_tag_handler_t) for the related CBOR format
see from_msgpack(InputType&&, const bool, const bool) for the related MessagePack format
see from_ubjson(InputType&&, const bool, const bool) for the related UBJSON format

Definition at line 25460 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

Referenced by from_bson().

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◆ from_bson() [4/4]

template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_bson ( IteratorType  first,
IteratorType  last,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

Create a JSON value from an input in BSON format.

Deserializes a given input i to a JSON value using the BSON (Binary JSON) serialization format.

The library maps BSON record types to JSON value types as follows:

BSON type BSON marker byte JSON value type
double 0x01 number_float
string 0x02 string
document 0x03 object
array 0x04 array
binary 0x05 binary
undefined 0x06 still unsupported
ObjectId 0x07 still unsupported
boolean 0x08 boolean
UTC Date-Time 0x09 still unsupported
null 0x0A null
Regular Expr. 0x0B still unsupported
DB Pointer 0x0C still unsupported
JavaScript Code 0x0D still unsupported
Symbol 0x0E still unsupported
JavaScript Code 0x0F still unsupported
int32 0x10 number_integer
Timestamp 0x11 still unsupported
128-bit decimal float 0x13 still unsupported
Max Key 0x7F still unsupported
Min Key 0xFF still unsupported
Warning
The mapping is incomplete. The unsupported mappings are indicated in the table above.
Parameters
[in]ian input in BSON format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.114if an unsupported BSON record type is encountered

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in BSON format to a JSON value.,from_bson}

See also
http://bsonspec.org/spec.html
see to_bson(const basic_json&) for the analogous serialization
see from_cbor(InputType&&, const bool, const bool, const cbor_tag_handler_t) for the related CBOR format
see from_msgpack(InputType&&, const bool, const bool) for the related MessagePack format
see from_ubjson(InputType&&, const bool, const bool) for the related UBJSON format

Definition at line 25476 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

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◆ from_cbor() [1/4]

template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_cbor ( const T *  ptr,
std::size_t  len,
const bool  strict = true,
const bool  allow_exceptions = true,
const cbor_tag_handler_t  tag_handler = cbor_tag_handler_t::error 
)
inlinestatic

Definition at line 25117 of file json.hpp.

References from_cbor().

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◆ from_cbor() [2/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_cbor ( detail::span_input_adapter &&  i,
const bool  strict = true,
const bool  allow_exceptions = true,
const cbor_tag_handler_t  tag_handler = cbor_tag_handler_t::error 
)
inlinestatic

◆ from_cbor() [3/4]

template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_cbor ( InputType &&  i,
const bool  strict = true,
const bool  allow_exceptions = true,
const cbor_tag_handler_t  tag_handler = cbor_tag_handler_t::error 
)
inlinestatic

create a JSON value from an input in CBOR format

Deserializes a given input i to a JSON value using the CBOR (Concise Binary Object Representation) serialization format.

The library maps CBOR types to JSON value types as follows:

CBOR type JSON value type first byte
Integer number_unsigned 0x00..0x17
Unsigned integer number_unsigned 0x18
Unsigned integer number_unsigned 0x19
Unsigned integer number_unsigned 0x1A
Unsigned integer number_unsigned 0x1B
Negative integer number_integer 0x20..0x37
Negative integer number_integer 0x38
Negative integer number_integer 0x39
Negative integer number_integer 0x3A
Negative integer number_integer 0x3B
Byte string binary 0x40..0x57
Byte string binary 0x58
Byte string binary 0x59
Byte string binary 0x5A
Byte string binary 0x5B
UTF-8 string string 0x60..0x77
UTF-8 string string 0x78
UTF-8 string string 0x79
UTF-8 string string 0x7A
UTF-8 string string 0x7B
UTF-8 string string 0x7F
array array 0x80..0x97
array array 0x98
array array 0x99
array array 0x9A
array array 0x9B
array array 0x9F
map object 0xA0..0xB7
map object 0xB8
map object 0xB9
map object 0xBA
map object 0xBB
map object 0xBF
False false 0xF4
True true 0xF5
Null null 0xF6
Half-Precision Float number_float 0xF9
Single-Precision Float number_float 0xFA
Double-Precision Float number_float 0xFB
Warning
The mapping is incomplete in the sense that not all CBOR types can be converted to a JSON value. The following CBOR types are not supported and will yield parse errors (parse_error.112):
  • date/time (0xC0..0xC1)
  • bignum (0xC2..0xC3)
  • decimal fraction (0xC4)
  • bigfloat (0xC5)
  • expected conversions (0xD5..0xD7)
  • simple values (0xE0..0xF3, 0xF8)
  • undefined (0xF7)
CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps with keys other than UTF-8 strings are rejected (parse_error.113).
Note
Any CBOR output created to_cbor can be successfully parsed by from_cbor.
Parameters
[in]ian input in CBOR format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
[in]tag_handlerhow to treat CBOR tags (optional, error by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.110if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112if unsupported features from CBOR were used in the given input v or if the input is not valid CBOR
parse_error.113if a string was expected as map key, but not found

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in CBOR format to a JSON value.,from_cbor}

See also
http://cbor.io
see to_cbor(const basic_json&) for the analogous serialization
see from_msgpack(InputType&&, const bool, const bool) for the related MessagePack format
see from_ubjson(InputType&&, const bool, const bool) for the related UBJSON format
Since
version 2.0.9; parameter start_index since 2.1.1; changed to consume input adapters, removed start_index parameter, and added strict parameter since 3.0.0; added allow_exceptions parameter since 3.2.0; added tag_handler parameter since 3.9.0.

Definition at line 25085 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

Referenced by from_cbor().

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◆ from_cbor() [4/4]

template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_cbor ( IteratorType  first,
IteratorType  last,
const bool  strict = true,
const bool  allow_exceptions = true,
const cbor_tag_handler_t  tag_handler = cbor_tag_handler_t::error 
)
inlinestatic

create a JSON value from an input in CBOR format

Deserializes a given input i to a JSON value using the CBOR (Concise Binary Object Representation) serialization format.

The library maps CBOR types to JSON value types as follows:

CBOR type JSON value type first byte
Integer number_unsigned 0x00..0x17
Unsigned integer number_unsigned 0x18
Unsigned integer number_unsigned 0x19
Unsigned integer number_unsigned 0x1A
Unsigned integer number_unsigned 0x1B
Negative integer number_integer 0x20..0x37
Negative integer number_integer 0x38
Negative integer number_integer 0x39
Negative integer number_integer 0x3A
Negative integer number_integer 0x3B
Byte string binary 0x40..0x57
Byte string binary 0x58
Byte string binary 0x59
Byte string binary 0x5A
Byte string binary 0x5B
UTF-8 string string 0x60..0x77
UTF-8 string string 0x78
UTF-8 string string 0x79
UTF-8 string string 0x7A
UTF-8 string string 0x7B
UTF-8 string string 0x7F
array array 0x80..0x97
array array 0x98
array array 0x99
array array 0x9A
array array 0x9B
array array 0x9F
map object 0xA0..0xB7
map object 0xB8
map object 0xB9
map object 0xBA
map object 0xBB
map object 0xBF
False false 0xF4
True true 0xF5
Null null 0xF6
Half-Precision Float number_float 0xF9
Single-Precision Float number_float 0xFA
Double-Precision Float number_float 0xFB
Warning
The mapping is incomplete in the sense that not all CBOR types can be converted to a JSON value. The following CBOR types are not supported and will yield parse errors (parse_error.112):
  • date/time (0xC0..0xC1)
  • bignum (0xC2..0xC3)
  • decimal fraction (0xC4)
  • bigfloat (0xC5)
  • expected conversions (0xD5..0xD7)
  • simple values (0xE0..0xF3, 0xF8)
  • undefined (0xF7)
CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps with keys other than UTF-8 strings are rejected (parse_error.113).
Note
Any CBOR output created to_cbor can be successfully parsed by from_cbor.
Parameters
[in]ian input in CBOR format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
[in]tag_handlerhow to treat CBOR tags (optional, error by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.110if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112if unsupported features from CBOR were used in the given input v or if the input is not valid CBOR
parse_error.113if a string was expected as map key, but not found

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in CBOR format to a JSON value.,from_cbor}

See also
http://cbor.io
see to_cbor(const basic_json&) for the analogous serialization
see from_msgpack(InputType&&, const bool, const bool) for the related MessagePack format
see from_ubjson(InputType&&, const bool, const bool) for the related UBJSON format
Since
version 2.0.9; parameter start_index since 2.1.1; changed to consume input adapters, removed start_index parameter, and added strict parameter since 3.0.0; added allow_exceptions parameter since 3.2.0; added tag_handler parameter since 3.9.0.

Definition at line 25102 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

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◆ from_msgpack() [1/4]

template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_msgpack ( const T *  ptr,
std::size_t  len,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

Definition at line 25260 of file json.hpp.

References from_msgpack().

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◆ from_msgpack() [2/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_msgpack ( detail::span_input_adapter &&  i,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

◆ from_msgpack() [3/4]

template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_msgpack ( InputType &&  i,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

create a JSON value from an input in MessagePack format

Deserializes a given input i to a JSON value using the MessagePack serialization format.

The library maps MessagePack types to JSON value types as follows:

MessagePack type JSON value type first byte
positive fixint number_unsigned 0x00..0x7F
fixmap object 0x80..0x8F
fixarray array 0x90..0x9F
fixstr string 0xA0..0xBF
nil null 0xC0
false false 0xC2
true true 0xC3
float 32 number_float 0xCA
float 64 number_float 0xCB
uint 8 number_unsigned 0xCC
uint 16 number_unsigned 0xCD
uint 32 number_unsigned 0xCE
uint 64 number_unsigned 0xCF
int 8 number_integer 0xD0
int 16 number_integer 0xD1
int 32 number_integer 0xD2
int 64 number_integer 0xD3
str 8 string 0xD9
str 16 string 0xDA
str 32 string 0xDB
array 16 array 0xDC
array 32 array 0xDD
map 16 object 0xDE
map 32 object 0xDF
bin 8 binary 0xC4
bin 16 binary 0xC5
bin 32 binary 0xC6
ext 8 binary 0xC7
ext 16 binary 0xC8
ext 32 binary 0xC9
fixext 1 binary 0xD4
fixext 2 binary 0xD5
fixext 4 binary 0xD6
fixext 8 binary 0xD7
fixext 16 binary 0xD8
negative fixint number_integer 0xE0-0xFF
Note
Any MessagePack output created to_msgpack can be successfully parsed by from_msgpack.
Parameters
[in]ian input in MessagePack format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.110if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112if unsupported features from MessagePack were used in the given input i or if the input is not valid MessagePack
parse_error.113if a string was expected as map key, but not found

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in MessagePack format to a JSON value.,from_msgpack}

See also
http://msgpack.org
see to_msgpack(const basic_json&) for the analogous serialization
see from_cbor(InputType&&, const bool, const bool, const cbor_tag_handler_t) for the related CBOR format
see from_ubjson(InputType&&, const bool, const bool) for the related UBJSON format
see from_bson(InputType&&, const bool, const bool) for the related BSON format
Since
version 2.0.9; parameter start_index since 2.1.1; changed to consume input adapters, removed start_index parameter, and added strict parameter since 3.0.0; added allow_exceptions parameter since 3.2.0

Definition at line 25229 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

Referenced by from_msgpack().

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◆ from_msgpack() [4/4]

template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_msgpack ( IteratorType  first,
IteratorType  last,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

create a JSON value from an input in MessagePack format

Deserializes a given input i to a JSON value using the MessagePack serialization format.

The library maps MessagePack types to JSON value types as follows:

MessagePack type JSON value type first byte
positive fixint number_unsigned 0x00..0x7F
fixmap object 0x80..0x8F
fixarray array 0x90..0x9F
fixstr string 0xA0..0xBF
nil null 0xC0
false false 0xC2
true true 0xC3
float 32 number_float 0xCA
float 64 number_float 0xCB
uint 8 number_unsigned 0xCC
uint 16 number_unsigned 0xCD
uint 32 number_unsigned 0xCE
uint 64 number_unsigned 0xCF
int 8 number_integer 0xD0
int 16 number_integer 0xD1
int 32 number_integer 0xD2
int 64 number_integer 0xD3
str 8 string 0xD9
str 16 string 0xDA
str 32 string 0xDB
array 16 array 0xDC
array 32 array 0xDD
map 16 object 0xDE
map 32 object 0xDF
bin 8 binary 0xC4
bin 16 binary 0xC5
bin 32 binary 0xC6
ext 8 binary 0xC7
ext 16 binary 0xC8
ext 32 binary 0xC9
fixext 1 binary 0xD4
fixext 2 binary 0xD5
fixext 4 binary 0xD6
fixext 8 binary 0xD7
fixext 16 binary 0xD8
negative fixint number_integer 0xE0-0xFF
Note
Any MessagePack output created to_msgpack can be successfully parsed by from_msgpack.
Parameters
[in]ian input in MessagePack format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.110if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112if unsupported features from MessagePack were used in the given input i or if the input is not valid MessagePack
parse_error.113if a string was expected as map key, but not found

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in MessagePack format to a JSON value.,from_msgpack}

See also
http://msgpack.org
see to_msgpack(const basic_json&) for the analogous serialization
see from_cbor(InputType&&, const bool, const bool, const cbor_tag_handler_t) for the related CBOR format
see from_ubjson(InputType&&, const bool, const bool) for the related UBJSON format
see from_bson(InputType&&, const bool, const bool) for the related BSON format
Since
version 2.0.9; parameter start_index since 2.1.1; changed to consume input adapters, removed start_index parameter, and added strict parameter since 3.0.0; added allow_exceptions parameter since 3.2.0

Definition at line 25245 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

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◆ from_ubjson() [1/4]

template<typename T >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_ubjson ( const T *  ptr,
std::size_t  len,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

Definition at line 25376 of file json.hpp.

References from_ubjson().

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◆ from_ubjson() [2/4]

static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_ubjson ( detail::span_input_adapter &&  i,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

◆ from_ubjson() [3/4]

template<typename InputType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_ubjson ( InputType &&  i,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

create a JSON value from an input in UBJSON format

Deserializes a given input i to a JSON value using the UBJSON (Universal Binary JSON) serialization format.

The library maps UBJSON types to JSON value types as follows:

UBJSON type JSON value type marker
no-op no value, next value is read N
null null Z
false false F
true true T
float32 number_float d
float64 number_float D
uint8 number_unsigned U
int8 number_integer i
int16 number_integer I
int32 number_integer l
int64 number_integer L
high-precision number number_integer, number_unsigned, or number_float - depends on number string 'H'
string string S
char string C
array array (optimized values are supported) [
object object (optimized values are supported) {
Note
The mapping is complete in the sense that any UBJSON value can be converted to a JSON value.
Parameters
[in]ian input in UBJSON format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.110if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112if a parse error occurs
parse_error.113if a string could not be parsed successfully

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in UBJSON format to a JSON value.,from_ubjson}

See also
http://ubjson.org
see to_ubjson(const basic_json&, const bool, const bool) for the analogous serialization
see from_cbor(InputType&&, const bool, const bool, const cbor_tag_handler_t) for the related CBOR format
see from_msgpack(InputType&&, const bool, const bool) for the related MessagePack format
see from_bson(InputType&&, const bool, const bool) for the related BSON format
Since
version 3.1.0; added allow_exceptions parameter since 3.2.0

Definition at line 25346 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

Referenced by from_ubjson().

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◆ from_ubjson() [4/4]

template<typename IteratorType >
static JSON_HEDLEY_WARN_UNUSED_RESULT basic_json nlohmann::basic_json::from_ubjson ( IteratorType  first,
IteratorType  last,
const bool  strict = true,
const bool  allow_exceptions = true 
)
inlinestatic

create a JSON value from an input in UBJSON format

Deserializes a given input i to a JSON value using the UBJSON (Universal Binary JSON) serialization format.

The library maps UBJSON types to JSON value types as follows:

UBJSON type JSON value type marker
no-op no value, next value is read N
null null Z
false false F
true true T
float32 number_float d
float64 number_float D
uint8 number_unsigned U
int8 number_integer i
int16 number_integer I
int32 number_integer l
int64 number_integer L
high-precision number number_integer, number_unsigned, or number_float - depends on number string 'H'
string string S
char string C
array array (optimized values are supported) [
object object (optimized values are supported) {
Note
The mapping is complete in the sense that any UBJSON value can be converted to a JSON value.
Parameters
[in]ian input in UBJSON format convertible to an input adapter
[in]strictwhether to expect the input to be consumed until EOF (true by default)
[in]allow_exceptionswhether to throw exceptions in case of a parse error (optional, true by default)
Returns
deserialized JSON value; in case of a parse error and allow_exceptions set to false, the return value will be value_t::discarded.
Exceptions
parse_error.110if the given input ends prematurely or the end of file was not reached when strict was set to true
parse_error.112if a parse error occurs
parse_error.113if a string could not be parsed successfully

@complexity Linear in the size of the input i.

@liveexample{The example shows the deserialization of a byte vector in UBJSON format to a JSON value.,from_ubjson}

See also
http://ubjson.org
see to_ubjson(const basic_json&, const bool, const bool) for the analogous serialization
see from_cbor(InputType&&, const bool, const bool, const cbor_tag_handler_t) for the related CBOR format
see from_msgpack(InputType&&, const bool, const bool) for the related MessagePack format
see from_bson(InputType&&, const bool, const bool) for the related BSON format
Since
version 3.1.0; added allow_exceptions parameter since 3.2.0

Definition at line 25362 of file json.hpp.

References basic_json(), nlohmann::detail::discarded, nlohmann::detail::input_adapter(), altar_valkyrie::res, rotate-tower::result, and nlohmann::detail::binary_reader< BasicJsonType, InputAdapterType, SAX >::sax_parse().

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◆ front() [1/2]

reference nlohmann::basic_json::front ( )
inline

access the first element

Returns a reference to the first element in the container. For a JSON container c, the expression c.front() is equivalent to *c.begin().

Returns
In case of a structured type (array or object), a reference to the first element is returned. In case of number, string, boolean, or binary values, a reference to the value is returned.

@complexity Constant.

Precondition
The JSON value must not be null (would throw std::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
Postcondition
The JSON value remains unchanged.
Exceptions
invalid_iterator.214when called on null value

@liveexample{The following code shows an example for front().,front}

See also
see back() – access the last element
Since
version 1.0.0

Definition at line 21471 of file json.hpp.

References begin().

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◆ front() [2/2]

const_reference nlohmann::basic_json::front ( ) const
inline

access the first element

Returns a reference to the first element in the container. For a JSON container c, the expression c.front() is equivalent to *c.begin().

Returns
In case of a structured type (array or object), a reference to the first element is returned. In case of number, string, boolean, or binary values, a reference to the value is returned.

@complexity Constant.

Precondition
The JSON value must not be null (would throw std::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
Postcondition
The JSON value remains unchanged.
Exceptions
invalid_iterator.214when called on null value

@liveexample{The following code shows an example for front().,front}

See also
see back() – access the last element
Since
version 1.0.0

Definition at line 21479 of file json.hpp.

References cbegin().

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◆ get() [1/2]

template<typename ValueTypeCV , typename ValueType = detail::uncvref_t<ValueTypeCV>>
auto nlohmann::basic_json::get ( ) const -> decltype(std::declval<const basic_json_t&>().template get_impl<ValueType>(detail::priority_tag<4>
inlinenoexcept

get a (pointer) value (explicit)

Performs explicit type conversion between the JSON value and a compatible value if required.

Template Parameters
ValueTypeCVthe provided value type
ValueTypethe returned value type
Returns
copy of the JSON value, converted to
Template Parameters
ValueTypeif necessary
Exceptions
whatjson_serializer<ValueType> from_json() method throws if conversion is required
Since
version 2.1.0

Definition at line 20573 of file json.hpp.

◆ get() [2/2]

template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::value, int >::type = 0>
auto nlohmann::basic_json::get ( ) -> decltype(std::declval<basic_json_t&>().template get_ptr<PointerType>())
inlinenoexcept

get a pointer value (explicit)

Explicit pointer access to the internally stored JSON value. No copies are made.

Warning
The pointer becomes invalid if the underlying JSON object changes.
Template Parameters
PointerTypepointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, number_unsigned_t, or number_float_t.
Returns
pointer to the internally stored JSON value if the requested pointer type PointerType fits to the JSON value; nullptr otherwise

@complexity Constant.

@liveexample{The example below shows how pointers to internal values of a JSON value can be requested. Note that no type conversions are made and a nullptr is returned if the value and the requested pointer type does not match.,get__PointerType}

See also
see get_ptr() for explicit pointer-member access
Since
version 1.0.0

Definition at line 20614 of file json.hpp.

◆ get_allocator()

static allocator_type nlohmann::basic_json::get_allocator ( )
inlinestatic

returns the allocator associated with the container

Definition at line 17703 of file json.hpp.

◆ get_binary() [1/2]

binary_t& nlohmann::basic_json::get_binary ( )
inline
Returns
reference to the binary value
Exceptions
type_error.302if the value is not binary
See also
see is_binary() to check if the value is binary
Since
version 3.8.0

Definition at line 20794 of file json.hpp.

References nlohmann::detail::type_error::create(), is_binary(), JSON_THROW, and type_name().

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◆ get_binary() [2/2]

const binary_t& nlohmann::basic_json::get_binary ( ) const
inline

Returns
reference to the binary value
Exceptions
type_error.302if the value is not binary
See also
see is_binary() to check if the value is binary
Since
version 3.8.0

Definition at line 20805 of file json.hpp.

References nlohmann::detail::type_error::create(), is_binary(), JSON_THROW, and type_name().

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◆ get_impl() [1/7]

boolean_t nlohmann::basic_json::get_impl ( boolean_t ) const
inlineprivate

get a boolean (explicit)

Definition at line 20208 of file json.hpp.

References nlohmann::detail::type_error::create(), is_boolean(), JSON_HEDLEY_LIKELY, JSON_THROW, m_value, and type_name().

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◆ get_impl() [2/7]

template<typename ValueType , detail::enable_if_t< detail::is_default_constructible< ValueType >::value &&detail::has_from_json< basic_json_t, ValueType >::value, int > = 0>
ValueType nlohmann::basic_json::get_impl ( detail::priority_tag< 0 >  ) const
inlineprivatenoexcept

get a value (explicit)

Explicit type conversion between the JSON value and a compatible value which is CopyConstructible and DefaultConstructible. The value is converted by calling the json_serializer<ValueType> from_json() method.

The function is equivalent to executing

ValueType ret;
return ret;

This overloads is chosen if:

Template Parameters
ValueTypethe returned value type
Returns
copy of the JSON value, converted to ValueType
Exceptions
whatjson_serializer<ValueType> from_json() method throws

@liveexample{The example below shows several conversions from JSON values to other types. There a few things to note: (1) Floating-point numbers can be converted to integers\, (2) A JSON array can be converted to a standard std::vector<short>\, (3) A JSON object can be converted to C++ associative containers such as std::unordered_map<std::string\, json>.,get__ValueType_const}

Since
version 2.1.0

Definition at line 20435 of file json.hpp.

References nlohmann::detail::from_json().

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◆ get_impl() [3/7]

template<typename ValueType , detail::enable_if_t< detail::has_non_default_from_json< basic_json_t, ValueType >::value, int > = 0>
ValueType nlohmann::basic_json::get_impl ( detail::priority_tag< 1 >  ) const
inlineprivatenoexcept

get a value (explicit); special case

Explicit type conversion between the JSON value and a compatible value which is not CopyConstructible and not DefaultConstructible. The value is converted by calling the json_serializer<ValueType> from_json() method.

The function is equivalent to executing

This overloads is chosen if:

Note
If json_serializer<ValueType> has both overloads of from_json(), this one is chosen.
Template Parameters
ValueTypethe returned value type
Returns
copy of the JSON value, converted to ValueType
Exceptions
whatjson_serializer<ValueType> from_json() method throws
Since
version 2.1.0

Definition at line 20477 of file json.hpp.

References nlohmann::detail::from_json().

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◆ get_impl() [4/7]

template<typename BasicJsonType , detail::enable_if_t< detail::is_basic_json< BasicJsonType >::value, int > = 0>
BasicJsonType nlohmann::basic_json::get_impl ( detail::priority_tag< 2 >  ) const
inlineprivate

get special-case overload

This overloads converts the current basic_json in a different basic_json type

Template Parameters
BasicJsonType== basic_json
Returns
a copy of *this, converted into BasicJsonType

@complexity Depending on the implementation of the called from_json() method.

Since
version 3.2.0

Definition at line 20502 of file json.hpp.

◆ get_impl() [5/7]

template<typename BasicJsonType , detail::enable_if_t< std::is_same< BasicJsonType, basic_json_t >::value, int > = 0>
basic_json nlohmann::basic_json::get_impl ( detail::priority_tag< 3 >  ) const
inlineprivate

get special-case overload

This overloads avoids a lot of template boilerplate, it can be seen as the identity method

Template Parameters
BasicJsonType== basic_json
Returns
a copy of *this

@complexity Constant.

Since
version 2.1.0

Definition at line 20525 of file json.hpp.

◆ get_impl() [6/7]

return nlohmann::basic_json::get_impl ( detail::priority_tag< 4 > {}  )

◆ get_impl() [7/7]

template<typename PointerType , detail::enable_if_t< std::is_pointer< PointerType >::value, int > = 0>
constexpr auto nlohmann::basic_json::get_impl ( detail::priority_tag< 4 >  ) const -> decltype(std::declval<const basic_json_t&>().template get_ptr<PointerType>())
inlineconstexprprivatenoexcept

get a pointer value (explicit)

get a pointer value (explicit) Explicit pointer access to the internally stored JSON value. No copies are made.

Warning
The pointer becomes invalid if the underlying JSON object changes.
Template Parameters
PointerTypepointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, number_unsigned_t, or number_float_t.
Returns
pointer to the internally stored JSON value if the requested pointer type PointerType fits to the JSON value; nullptr otherwise

@complexity Constant.

@liveexample{The example below shows how pointers to internal values of a JSON value can be requested. Note that no type conversions are made and a nullptr is returned if the value and the requested pointer type does not match.,get__PointerType}

See also
see get_ptr() for explicit pointer-member access
Since
version 1.0.0

Definition at line 20538 of file json.hpp.

◆ get_impl_ptr() [1/16]

array_t* nlohmann::basic_json::get_impl_ptr ( array_t )
inlineprivatenoexcept

get a pointer to the value (array)

Definition at line 20231 of file json.hpp.

References is_array(), and m_value.

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◆ get_impl_ptr() [2/16]

binary_t* nlohmann::basic_json::get_impl_ptr ( binary_t )
inlineprivatenoexcept

get a pointer to the value (binary)

Definition at line 20303 of file json.hpp.

References is_binary(), and m_value.

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◆ get_impl_ptr() [3/16]

boolean_t* nlohmann::basic_json::get_impl_ptr ( boolean_t )
inlineprivatenoexcept

get a pointer to the value (boolean)

Definition at line 20255 of file json.hpp.

References is_boolean(), and m_value.

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