object

`object`

A dynamically sized associative container of JSON key/value pairs.

Synopsis

Defined in header <boost/json/object.hpp>.

class object;

Types

Name Description

Name	Description
`allocator_type`	Associated Allocator
`const_iterator`	A const random access iterator to an element.
`const_pointer`	A const pointer to an element.
`const_reference`	A const reference to an element.
`const_reverse_iterator`	A const reverse random access iterator to an element.
`difference_type`	The type used to represent signed integers.
`iterator`	A random access iterator to an element.
`key_type`	The type of keys.
`mapped_type`	The type of mapped values.
`pointer`	A pointer to an element.
`reference`	A reference to an element.
`reverse_iterator`	A reverse random access iterator to an element.
`size_type`	The type used to represent unsigned integers.
`value_type`	The element type.

allocator_type

Associated Allocator

const_iterator

A const random access iterator to an element.

const_pointer

A const pointer to an element.

const_reference

A const reference to an element.

const_reverse_iterator

A const reverse random access iterator to an element.

difference_type

The type used to represent signed integers.

iterator

A random access iterator to an element.

key_type

The type of keys.

mapped_type

The type of mapped values.

pointer

A pointer to an element.

reference

A reference to an element.

reverse_iterator

A reverse random access iterator to an element.

size_type

The type used to represent unsigned integers.

value_type

The element type.

Member Functions

Name Description

Name	Description
`at`	Access the specified element, with bounds checking.
`begin`	Return an iterator to the first element.
`capacity`	Return the number of elements that can be held in currently allocated memory.
`cbegin`	Return a const iterator to the first element.
`cend`	Return a const iterator to the element following the last element.
`clear`	Erase all elements.
`contains`	Return `true` if the key is found.
`count`	Count the number of elements with a specific key.
`crbegin`	Return a const reverse iterator to the first element of the reversed container.
`crend`	Return a const reverse iterator to the element following the last element of the reversed container.
`emplace`	Construct an element in-place.
`empty`	Return whether there are no elements.
`end`	Return an iterator to the element following the last element.
`erase`	Erase an element.
`find`	Find an element with a specific key.
`get_allocator`	Return the associated allocator.
`if_contains`	Return a pointer to the value if the key is found, or null.
`insert`	Insert elements.
`insert_or_assign`	Insert an element or assign to the current element if the key already exists.
`object` [constructor]	Default constructor.
`operator=`	Copy assignment.
`operator[]`	Access or insert the specified element.
`rbegin`	Return a reverse iterator to the first element of the reversed container.
`rend`	Return a reverse iterator to the element following the last element of the reversed container.
`reserve`	Increase the capacity to at least a certain amount.
`size`	Return the number of elements.
`stable_erase`	Erase an element preserving order.
`storage`	Return the associated memory resource.
`swap`	Swap two objects.
`try_at`	Access the specified element, with bounds checking.
`~object` [destructor]	Destructor.

at

Access the specified element, with bounds checking.

begin

Return an iterator to the first element.

capacity

Return the number of elements that can be held in currently allocated memory.

cbegin

Return a const iterator to the first element.

cend

Return a const iterator to the element following the last element.

clear

Erase all elements.

contains

Return true if the key is found.

count

Count the number of elements with a specific key.

crbegin

Return a const reverse iterator to the first element of the reversed container.

crend

Return a const reverse iterator to the element following the last element of the reversed container.

emplace

Construct an element in-place.

empty

Return whether there are no elements.

end

Return an iterator to the element following the last element.

erase

Erase an element.

find

Find an element with a specific key.

get_allocator

Return the associated allocator.

if_contains

Return a pointer to the value if the key is found, or null.

insert

Insert elements.

insert_or_assign

Insert an element or assign to the current element if the key already exists.

object [constructor]

Default constructor.

operator=

Copy assignment.

operator[]

Access or insert the specified element.

rbegin

Return a reverse iterator to the first element of the reversed container.

rend

Return a reverse iterator to the element following the last element of the reversed container.

reserve

Increase the capacity to at least a certain amount.

size

Return the number of elements.

stable_erase

Erase an element preserving order.

storage

Return the associated memory resource.

swap

Swap two objects.

try_at

Access the specified element, with bounds checking.

~object [destructor]

Destructor.

Static Member Functions

Name Description

Name	Description
`max_size`	Return the maximum number of elements any object can hold.

max_size

Return the maximum number of elements any object can hold.

Friends

Name Description

Name	Description
`operator!=`	Return `true` if two objects are not equal.
`operator<<`	Serialize `object` to an output stream.
`operator==`	Return `true` if two objects are equal.
`swap`	Swap two objects.

operator!=

Return true if two objects are not equal.

operator<<

Serialize object to an output stream.

operator==

Return true if two objects are equal.

swap

Swap two objects.

Description

This is an associative container whose elements are key/value pairs with unique keys.

The elements are stored contiguously; iterators are ordinary pointers, allowing random access pointer arithmetic for retrieving elements. In addition, the container maintains an internal index to speed up find operations, reducing the average complexity for most lookups and insertions.

Reallocations are usually costly operations in terms of performance, as elements are copied and the internal index must be rebuilt. The reserve function can be used to eliminate reallocations if the number of elements is known beforehand.

Allocators

All elements stored in the container, and their children if any, will use the same memory resource that was used to construct the container.

Thread Safety

Non-const member functions may not be called concurrently with any other member functions.

Satisfies

ContiguousContainer, ReversibleContainer, and SequenceContainer.

Convenience header <boost/json.hpp>.

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