a class to store JSON values

Synopsis

Declared in <nlohmann/json.hpp>

template<
    template<
    typename U,
    typename V,
    typename... Args> typename ObjectType = map,
    template<
    typename U,
    typename... Args> typename ArrayType = vector,
    class StringType = std::string,
    class BooleanType = bool,
    class NumberIntegerType = int64_t,
    class NumberUnsignedType = uint64_t,
    class NumberFloatType = double,
    template<typename U> typename AllocatorType = allocator,
    template<
    typename T,
    typename SFINAE = void> typename JSONSerializer = adl_serializer,
    class BinaryType = std::vector<uint8_t>,
    class CustomBaseClass = void>
class basic_json
    : public /* implementation-defined */::json_base_class<CustomBaseClass>

Description

a class to store JSON values

Base Classes

Name

Description

/* implementation-defined */::json_base_class<CustomBaseClass>

Type Aliases

Name

Description

allocator_type

the allocator type

array_t

a type for an array

binary_t

a type for a packed binary type

bjdata_version_t

how to encode BJData

boolean_t

a type for a boolean

cbor_tag_handler_t

how to treat CBOR tags

const_iterator

a const iterator for a basic_json container

const_pointer

the type of an element const pointer

const_reference

the type of an element const reference

const_reverse_iterator

a const reverse iterator for a basic_json container

default_object_comparator_t

default object key comparator type The actual object key comparator type (object_comparator_t) may be different.

difference_type

a type to represent differences between iterators

error_handler_t

how to treat decoding errors

exception

exception base class, see nlohmann::detail::exception

initializer_list_t

helper type for initializer lists of basic_json values

input_format_t

the supported input formats for the sax_parse function

invalid_iterator

exception indicating errors with iterators

iterator

an iterator for a basic_json container

json_pointer

JSON Pointer, see nlohmann::json_pointer

json_sax_t

SAX interface type, see nlohmann::json_sax

json_serializer

the type used to serialize/deserialize values of type T, see nlohmann::adl_serializer

number_float_t

a type for a number (floating‐point)

number_integer_t

a type for a number (integer)

number_unsigned_t

a type for a number (unsigned)

object_comparator_t

object key comparator type

object_t

a type for an object

other_error

exception indicating other library errors

out_of_range

exception indicating access out of the defined range

parse_error

exception indicating a parse error

parse_event_t

parser event types

parser_callback_t

per‐element parser callback type

pointer

the type of an element pointer

reference

the type of an element reference

reverse_iterator

a reverse iterator for a basic_json container

size_type

a type to represent container sizes

string_t

a type for a string

type_error

exception indicating executing a member function with a wrong type

value_t

the type of an element's value, see nlohmann::detail::value_t

value_type

the type of elements in a basic_json container

Member Functions

Name

Description

basic_json [constructor]

copy constructor

basic_json [constructor]

move constructor

basic_json [constructor]

create a null object

basic_json [constructor]

create an empty value with a given type

basic_json [constructor]

create a JSON value from an existing one

basic_json [constructor]

create a JSON value from a json_ref wrapper

basic_json [constructor]

create a JSON value from compatible types

basic_json [constructor]

construct an array with count copies of given value

basic_json [constructor]

construct a JSON container given an iterator range

basic_json [constructor]

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

~basic_json [destructor]

destructor

operator=

copy assignment

at

access specified array element with bounds checking

at

access specified array element with bounds checking

at

access specified element via JSON Pointer, with bounds checking

at

access specified element via JSON Pointer, with bounds checking

at

access specified object element with bounds checking

at

access specified object element with bounds checking

at [deprecated]

access specified element via JSON Pointer, with bounds checking

at [deprecated]

access specified element via JSON Pointer, with bounds checking

at

access specified object element with bounds checking

at

access specified object element with bounds checking

back

access the last element

back

access the last element

begin

returns an iterator to the first element

begin

returns an iterator to the first element

cbegin

returns a const iterator to the first element

cend

returns an iterator to one past the last element

clear

clears the contents

contains

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

contains

check the existence of an element in a JSON object

contains [deprecated]

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

contains

check the existence of an element in a JSON object

count

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

count

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

crbegin

returns a const reverse iterator to the last element

crend

returns a const reverse iterator to one before the first

dump

serialization

emplace

add an object to an object if key does not exist

emplace_back

add an object to an array

empty

checks whether the container is empty.

end

returns an iterator to one past the last element

end

returns an iterator to one past the last element

erase

remove element from a JSON array given an index

erase

remove element from a JSON object given a key

erase

remove element given an iterator

erase

remove element from a JSON object given a key

erase

remove elements given an iterator range

find

find an element in a JSON object

find

find an element in a JSON object

find

find an element in a JSON object

find

find an element in a JSON object

flatten

return flattened JSON value

front

access the first element

front

access the first element

get

get a pointer value (explicit)

get

get a (pointer) value (explicit)

get_binary

get a binary value

get_binary

get a binary value

get_ptr

get a pointer value (implicit)

get_ptr

get a pointer value (implicit)

get_ref

get a reference value (implicit)

get_ref

get a reference value (implicit)

get_to

get a value (explicit)

get_to

get a value (explicit)

get_to

get a value (explicit)

insert

inserts range of elements into object

insert

inserts elements from initializer list into array

insert

inserts element into array

insert

inserts element into array

insert

inserts range of elements into array

insert

inserts copies of element into array

insert_iterator

helper for insertion of an iterator

is_array

return whether value is an array

is_binary

return whether value is a binary array

is_boolean

return whether value is a boolean

is_discarded

return whether value is discarded

is_null

return whether value is null

is_number

return whether value is a number

is_number_float

return whether value is a floating‐point number

is_number_integer

return whether value is an integer number

is_number_unsigned

return whether value is an unsigned integer number

is_object

return whether value is an object

is_primitive

return whether type is primitive

is_string

return whether value is a string

is_structured

return whether type is structured

items

helper to access iterator member functions in range‐based for

items

helper to access iterator member functions in range‐based for

max_size

returns the maximum possible number of elements

merge_patch

applies a JSON Merge Patch

operator+=

add an object to an object

operator+=

add an object to an array

operator+=

add an object to an object

operator+=

add an object to an array

operator[]

access specified object element

operator[]

access specified array element

operator[]

access specified array element

operator[]

access specified element via JSON Pointer

operator[]

access specified element via JSON Pointer

operator[]

access specified object element

operator[] [deprecated]

access specified element via JSON Pointer

operator[] [deprecated]

access specified element via JSON Pointer

operator[]

access specified object element

operator[]

access specified object element

operator[]

access specified object element

operator[]

access specified object element

patch

applies a JSON patch to a copy of the current object

patch_inplace

applies a JSON patch in‐place without copying the object

push_back

add an object to an object

push_back

add an object to an array

push_back

add an object to an object

push_back

add an object to an array

rbegin

returns an iterator to the reverse‐beginning

rbegin

returns an iterator to the reverse‐beginning

rend

returns an iterator to the reverse‐end

rend

returns an iterator to the reverse‐end

size

returns the number of elements

swap

exchanges the values

swap

exchanges the values

swap

exchanges the values

swap

exchanges the values

swap

exchanges the values

swap

exchanges the values

type

return the type of the JSON value (explicit)

type_name

return the type as string

unflatten

unflatten a previously flattened JSON value

update

updates a JSON object from another object, overwriting existing keys

update

updates a JSON object from another object, overwriting existing keys

value

access specified object element via JSON Pointer with default value

value

access specified object element with default value

value

access specified object element via JSON Pointer with default value

value

access specified object element with default value

value [deprecated]

access specified object element via JSON Pointer with default value

value

access specified object element with default value

value [deprecated]

access specified object element via JSON Pointer with default value

value

access specified object element with default value

operator ValueType

get a value (implicit)

operator value_t

return the type of the JSON value (implicit)

operator==

comparison: equal

operator==

comparison: equal

operator<=>

comparison: 3‐way

operator<=>

comparison: 3‐way

Static Member Functions

Name

Description

accept [deprecated]

check if the input is valid JSON

accept

check if the input is valid JSON

accept

check if the input is valid JSON (iterator pair, or iterator+sentinel pair for C++20 ranges support)

array

explicitly create an array from an initializer list

binary

explicitly create a binary array (without subtype)

binary

explicitly create a binary array

binary

explicitly create a binary array (with subtype)

binary

explicitly create a binary array (with subtype)

diff

creates a diff as a JSON patch

from_bjdata

create a JSON value from an input in BJData format

from_bjdata

create a JSON value from an input in BJData format (iterator pair, or iterator+sentinel pair for C++20 ranges support)

from_bson [deprecated]

create a JSON value from an input in BSON format

from_bson

create a JSON value from an input in BSON format

from_bson [deprecated]

create a JSON value from an input in BSON format

from_bson

create a JSON value from an input in BSON format (iterator pair, or iterator+sentinel pair for C++20 ranges support)

from_cbor [deprecated]

create a JSON value from an input in CBOR format

from_cbor

create a JSON value from an input in CBOR format

from_cbor [deprecated]

create a JSON value from an input in CBOR format

from_cbor

create a JSON value from an input in CBOR format (iterator pair, or iterator+sentinel pair for C++20 ranges support)

from_msgpack [deprecated]

create a JSON value from an input in MessagePack format

from_msgpack

create a JSON value from an input in MessagePack format

from_msgpack [deprecated]

create a JSON value from an input in MessagePack format

from_msgpack

create a JSON value from an input in MessagePack format (iterator pair, or iterator+sentinel pair for C++20 ranges support)

from_ubjson [deprecated]

create a JSON value from an input in UBJSON format

from_ubjson

create a JSON value from an input in UBJSON format

from_ubjson [deprecated]

create a JSON value from an input in UBJSON format

from_ubjson

create a JSON value from an input in UBJSON format (iterator pair, or iterator+sentinel pair for C++20 ranges support)

get_allocator

returns the allocator associated with the container

iterator_wrapper [deprecated]

wrapper to access iterator member functions in range‐based for

iterator_wrapper [deprecated]

wrapper to access iterator member functions in range‐based for

meta

returns version information on the library

object

explicitly create an object from an initializer list

parse [deprecated]

deserialize from a compatible input

parse

deserialize from a compatible input

parse

deserialize from a pair of character iterators (or an iterator+sentinel pair, C++20 ranges support)

sax_parse [deprecated]

generate SAX events

sax_parse

generate SAX events

sax_parse

generate SAX events (iterator pair, or iterator+sentinel pair for C++20 ranges support)

to_bjdata

create a BJData serialization of a given JSON value

to_bjdata

create a BJData serialization of a given JSON value

to_bjdata

create a BJData serialization of a given JSON value

to_bson

create a BSON serialization of a given JSON value

to_bson

create a BSON serialization of a given JSON value

to_bson

create a BSON serialization of a given JSON value

to_cbor

create a CBOR serialization of a given JSON value

to_cbor

create a CBOR serialization of a given JSON value

to_cbor

create a CBOR serialization of a given JSON value

to_msgpack

create a MessagePack serialization of a given JSON value

to_msgpack

create a MessagePack serialization of a given JSON value

to_msgpack

create a MessagePack serialization of a given JSON value

to_ubjson

create a UBJSON serialization of a given JSON value

to_ubjson

create a UBJSON serialization of a given JSON value

to_ubjson

create a UBJSON serialization of a given JSON value

Friends

Name

Description

nlohmann::operator>>

deserialize from stream

nlohmann::operator<<

deserialize from stream

nlohmann::operator>>

serialize to stream

nlohmann::operator<<

serialize to stream

nlohmann::swap

exchanges the values

nlohmann::detail::exception

general exception of the basic_json class

nlohmann::detail::serializer

nlohmann::json_pointer

JSON Pointer defines a string syntax for identifying a specific value within a JSON document

Non-Member Functions

Name

Description

format_as

user‐defined format_as function for JSON values (fmt <= 11.0.x support)

operator<<

deserialize from stream

operator>>

serialize to stream

to_string

user‐defined to_string function for JSON values

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