#include <jsoncons/basic_json.hpp>
template<
class CharT,
class Policy = sorted_policy,
class Allocator = std::allocator<char>
> class basic_json;
namespace pmr {
template <typename CharT,typename Policy>
using basic_json = jsoncons::basic_json<CharT, Policy, std::pmr::polymorphic_allocator<char>>;
using json = basic_json<char,sorted_policy>; (since 0.171.0)
using wjson = basic_json<wchar_t,sorted_policy>;
using ojson = basic_json<char, order_preserving_policy>;
using wojson = basic_json<wchar_t, order_preserving_policy>;
}A basic_json is a union type that can hold one of a number of possible data members,
some that require an allocator (a long string, byte string, array, or object),
and other trivially copyable ones that do not (an empty object, short string, number, boolean, or null).
The data member may be tagged with a semantic_tag that provides additional
information about its value. The sizeof a basic_json regardless of its template parameters
is normally 16 bytes.
A basic_json is allocator-aware, and supports allocator propagation to allocator-aware arrays
or objects. Every constructor has a version that accepts an allocator argument.
A long string, byte string, array or object contains a pointer to underlying storage,
the allocator is used to allocate that storage, and it is retained in that storage.
For other data members the allocator argument is ignored. For more about allocators,
see Allocators.
When assigned a new basic_json value, the old value is overwritten. The member data type of the new value may be different
from the old value.
A basic_json can support multiple readers concurrently, as long as it is not being modified.
If it is being modified, it must be by one writer with no concurrent readers.
Several aliases for common character types and policies for ordering an object's name/value pairs are provided:
| Type | Definition |
|---|---|
| jsoncons::json | jsoncons::basic_json<char,jsoncons::sorted_policy,std::allocator<char>> |
| jsoncons::ojson | jsoncons::basic_json<char,jsoncons::order_preserving_policy,std::allocator<char>> |
| jsoncons::wjson | jsoncons::basic_json<wchar_t,jsoncons::jsoncons::sorted_policy,std::allocator<char>> |
| jsoncons::wojson | jsoncons::basic_json<wchar_t,jsoncons::order_preserving_policy,std::allocator<char>> |
jsoncons::pmr::json (0.171.0) |
jsoncons::pmr::basic_json<char,jsoncons::sorted_policy> |
jsoncons::pmr::ojson (0.171.0) |
jsoncons::pmr::basic_json<char,jsoncons::order_preserving_policy> |
jsoncons::pmr::wjson (0.171.0) |
jsoncons::pmr::basic_json<wchar_t,jsoncons::sorted_policy> |
jsoncons::pmr::wojson (0.171.0) |
jsoncons::pmr::basic_json<wchar_t,jsoncons::order_preserving_policy> |
| CharT | Character type of text string |
| Policy | Implementation policy for arrays and objects |
| Allocator | Allocator type for allocating internal storage for long strings, byte strings, arrays and objects.
The allocator type may be a stateless allocator, a std::pmr::polymorphic_allocator,
or a std::scoped_allocator_adaptor.
Non-propagating stateful allocators, such as the Boost.Interprocess allocators,
must be wrapped by a std::scoped_allocator_adaptor. |
| Member type | Definition |
|---|---|
char_type |
CharT |
policy_type |
Policy |
allocator_type (until 0.171.0) |
A stateless allocator, or a non-propagating stateful allocator |
allocator_type (after 0.171.0) |
A stateless allocator, std::pmr::polymorphic_allocator, or std::scoped_allocator_adaptor |
char_traits_type |
std::char_traits<char_type> |
char_allocator_type |
allocator_type rebound to char_type |
reference |
basic_json& |
const_reference |
const basic_json& |
pointer |
basic_json* |
const_pointer |
const basic_json* |
string_view_type |
basic_string_view<char_type> |
key_type |
A ContiguousContainer to char_type |
key_value_type |
key_value<key_type,basic_json> |
object_iterator |
A RandomAccessIterator to key_value_type |
const_object_iterator |
A const RandomAccessIterator to const key_value_type |
array_iterator |
A RandomAccessIterator to basic_json |
const_array_iterator |
A const RandomAccessIterator to const basic_json |
object_range_type |
range<object_iterator,const_array_iterator> (since 0.173.3) |
const_object_range_type |
range<const_object_iterator,const_array_iterator> (since 0.173.3) |
array_range_type |
range<array_iterator,const_array_iterator> (since 0.173.3) |
const_array_range_type |
range<const_array_iterator,const_array_iterator> (since 0.173.3) |
proxy_type |
proxy<basic_json>. The proxy_type class supports conversion to basic_json&. (removed in 1.0.0) |
| parse | Parses JSON. |
| make_array | Makes a multidimensional basic_json array. |
| const basic_json& null() | Returns a null value |
| (constructor) | constructs the basic_json value |
| (destructor) | destructs the basic_json value |
| operator= | assigns values |
allocator_type get_allocator() const
For a long string, byte string, array, or object, returns the retained allocator used to allocate memory for their storage, otherwise attempts to return a default constructed allocator.
| array_range | Returns a range that supports a range-based for loop over the elements of a basic_json array. |
| obect_range | Returns a range that supports a range-based for loop over the key-value pairs of a basic_json object. |
| size_t size() const noexcept | Returns the number of elements in a basic_json array, or the number of members in a object, or |
| bool empty() const noexcept | Returns true if a basic_json string, object or array has no elements, otherwise false |
| size_t capacity() const | Returns the size of the storage space currently allocated for a basic_json object or array |
| void reserve(std::size_t n) | Increases the capacity of a basic_json object or array to allow at least n members or elements |
| void resize(std::size_t n) | Resizes a basic_json array so that it contains n elements |
| void resize(std::size_t n, const basic_json& val) | Resizes a basic_json array so that it contains n elements that are initialized to val |
| void shrink_to_fit() | Requests the removal of unused capacity |
| bool contains(const string_view_type& key) const noexcept | Returns true if an object has a member with the given key , otherwise false |
| is | Checks if a basic_json value matches a type. |
| as | Attempts to convert a basic_json value to a value of a type. |
| operator[] | Access or insert specified element. |
| at at_or_null |
Return the specified value. |
| get_value_or | Return the specified value if available, otherwise a default value. |
semantic_tag tag() const
Returns the semantic_tag associated with this value
uint64_t ext_tag() const
If tag() == semantic_tag::ext, returns a format specific tag associated with a byte string value,
otherwise return 0. An example is a MessagePack type in the range 0-127 associated with the
MessagePack ext format family, or a CBOR tag preceeding a byte string.
json_type type() const
Returns the json type associated with this value
object_iterator find(const string_view_type& name)
const_object_iterator find(const string_view_type& name) const
Returns an object iterator to a member whose name compares equal to name. If there is no such member, returns object_range.end().
Throws std::domain_error if not an object.
| void clear() | Remove all elements from an array or members from an object, otherwise do nothing |
| erase | Erases array elements and object members |
| push_back | Adds a value to the end of a basic_json array |
| insert | Inserts elements |
| emplace_back | Constructs a value in place at the end of a basic_json array |
| emplace | Constructs a value in place before a specified position in a basic_json array |
| try_emplace | Constructs a key-value pair in place in a basic_json object if the key does not exist, does nothing if the key exists |
| insert_or_assign | Inserts a key-value pair in a basic_json object if the key does not exist, or assigns a new value if the key already exists |
| merge | Inserts another basic_json object's key-value pairs into a basic_json object, if they don't already exist. |
| merge_or_update | Inserts another basic_json object's key-value pairs into a basic_json object, or assigns them if they already exist. |
| void swap(basic_json& val) noexcept | Exchanges the content of the basic_json value with the content of val, which is another basic_json value |
| dump | Serializes basic_json value to a string, stream, or basic_json_visitor. |
bool operator==(const basic_json& lhs, const basic_json& rhs)
Returns true if two basic_json objects compare equal, false otherwise.
bool operator!=(const basic_json& lhs, const basic_json& rhs)
Returns true if two basic_json objects do not compare equal, false otherwise.
bool operator<(const basic_json& lhs, const basic_json& rhs)
Compares the contents of lhs and rhs lexicographically.
bool operator<=(const basic_json& lhs, const basic_json& rhs)
Compares the contents of lhs and rhs lexicographically.
bool operator>(const basic_json& lhs, const basic_json& rhs)
Compares the contents of lhs and rhs lexicographically.
bool operator>=(const basic_json& lhs, const basic_json& rhs)
Compares the contents of lhs and rhs lexicographically.
std::basic_istream<char_type>& operator>>(std::basic_istream<char_type>& is, basic_json& o)
Reads a basic_json value from a stream.
std::basic_ostream<char_type>& operator<<(std::basic_ostream<char_type>& os, const basic_json& o)
Inserts basic_json value into stream.
std::basic_ostream<char_type>& print(const basic_json& val)
std::basic_ostream<char_type>& print(const basic_json& val, const basic_json_options<CharT>& options)
Inserts basic_json value into stream using the specified basic_json_options if supplied.
std::basic_ostream<char_type>& pretty_print(const basic_json& val)
std::basic_ostream<char_type>& pretty_print(const basic_json& val, const basic_json_options<CharT>& options)
Inserts basic_json value into stream using the specified basic_json_options if supplied.
void swap(basic_json& a, basic_json& b) noexcept
Exchanges the values of a and b