#include <jsoncons/basic_json.hpp>
template<
class CharT,
class Policy = sorted_policy,
class Allocator = std::allocator<char>
> class basic_json;
namespace pmr {
template<class CharT, class 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>;
}The class basic_json resembles a union. A basic_json holds a data item of one of its alternative types:
null, bool, int64_t, uint64_t, double, text string, byte string, array, and object. The data item may be tagged with a
semantic_tag that provides additional information about the data item.
When assigned a new basic_json value, the old value is overwritten. The type of the new value may be different from the old value.
The definition of the character type of text strings is supplied via the CharT template parameter.
Implementation policies for arrays and objects are provided via the Policy template parameter.
A custom allocator may be supplied with the Allocator template parameter, which a basic_json will
rebind to internal data structures.
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.
Since 0.171.0, basic_json supports std::uses_allocator construction.
The allocator template parameter 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.
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> |
| 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&. |
| 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
Returns the allocator associated with the basic_json value.
| 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