constexpr basic_json(); (1)
basic_json(const basic_json& other); (2)
basic_json(const basic_json& other, const allocator_type& alloc); (3)
basic_json(basic_json&& other) noexcept; (4)
basic_json(basic_json&& other, const allocator_type& alloc) noexcept; (5)
template <class T>
basic_json(const T& val); (6)
template <class Unsigned>
constexpr basic_json(Unsigned val, semantic_tag tag); (7)
template <class Signed>
constexpr basic_json(Signed val, semantic_tag tag); (8)
constexpr basic_json(half_arg_t, uint16_t value,
semantic_tag tag = semantic_tag::none); (9)
constexpr basic_json(double val, semantic_tag tag); (10)
explicit basic_json(json_object_arg_t,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (11)
template<class InputIt>
basic_json(json_object_arg_t,
InputIt first, InputIt last,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (12)
basic_json(json_object_arg_t,
std::initializer_list<std::pair<std::basic_string<char_type>,basic_json>> init,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (13)
explicit basic_json(json_array_arg_t,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (14)
template<class InputIt>
basic_json(json_array_arg_t,
InputIt first, InputIt last,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (15)
basic_json(json_array_arg_t,
std::initializer_list<basic_json> init,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (16)
template <class T>
basic_json(const T& val, const allocator_type& alloc); (17)
basic_json(const char_type* val); (18)
basic_json(const char_type* val, const allocator_type& alloc); (19)
basic_json(const byte_string_view& bytes,
semantic_tag tag,
const Allocator& alloc = Allocator()); (20)
basic_json(byte_string_arg_t, const jsoncons::span<const uint8_t>& bytes,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (21) (until 0.152)
template <class Source>
basic_json(byte_string_arg_t, const Source& source,
semantic_tag tag = semantic_tag::none,
const Allocator& alloc = Allocator()); (21) (since 0.152)
template <class Source>
basic_json(byte_string_arg_t, const Source& source,
uint64_t ext_tag,
const Allocator& alloc = Allocator()); (22) (since 0.152)
basic_json(json_const_pointer_arg, const basic_json* j_ptr); (23) (since 0.156.0)(1) Constructs an empty json object.
(2) Constructs a copy of val
(3) Copy with allocator
(4) Acquires the contents of val, leaving val a null value
(5) Move with allocator
(6) Constructs a basic_json value for types supported in json_type_traits.
(7) Constructs a basic_json value from an unsigned integer and a semantic_tag. This overload only participates in overload resolution if Unsigned is an unsigned integral type.
(8) Constructs a basic_json value from a signed integer and a semantic_tag. This overload only participates in overload resolution if Signed is a signed integral type.
(9) Constructs a basic_json value for a half precision floating point number.
Uses half_arg_t as first argument to disambiguate overloads that construct half precision floating point numbers.
(10) Constructs a basic_json value from a double and a semantic_tag.
(11)-(12) use json_object_arg_t as first argument to disambiguate overloads that construct json objects.
(11) Constructs a json object with the provided semantic_tag and allocator.
(12) Constructs a json object with the contents of the range [first,last].
(13) Constructs a json object with the contents of the initializer list init.
(14)-(16) use json_array_arg_t as first argument to disambiguate overloads that construct json objects.
(14) Constructs a json array with the provided semantic_tag and allocator.
(15) Constructs a json array with the contents of the range [first,last].
std::iterator_traits<InputIt>::value_type must be convertible to basic_json.
(16) Constructs a json array with the contents of the initializer list init.
(17) Constructs a basic_json value for types supported in json_type_traits with allocator.
(18) Constructs a basic_json value from a text string.
(19) Constructs a basic_json value from a text string with supplied allocator.
(20) Constructs a basic_json value from a byte_string_view.
(21) Constructs a basic_json value for a byte string from a contiguous byte sequence provided by source
with a generic tag.
Type Source must be a contiguous container that has member functions data() and size(), and member type value_type
with width of exactly 8 bits (since 0.152.0.)
Any of the values types int8_t, uint8_t, char, unsigned char and std::byte (since C++17) are allowed.
Uses byte_string_arg_t as first argument to disambiguate overloads that construct byte strings.
(22) Constructs a basic_json value for a byte string from a contiguous byte sequence provided by source
with a format specific tag.
Type Source must be a contiguous container that has member functions data() and size(), and member type value_type
with width of exactly 8 bits (since 0.152.0.)
Any of the values types int8_t, uint8_t, char, unsigned char and std::byte (since C++17) are allowed.
Uses byte_string_arg_t as first argument to disambiguate overloads that construct byte strings.
(23) Constructs a basic_json value that provides a non-owning view of
another basic_json value. If second argument j_ptr is null,
constructs a null value.
| Helper | Definition |
|---|---|
| [json_object_arg][../json_object_arg.md] | |
| [json_object_arg_t][../json_object_arg_t.md] | json object construction tag |
| [json_array_arg][../json_array_arg.md] | |
| [json_array_arg_t][../json_array_arg_t.md] | json array construction tag |
| [byte_string_arg][../byte_string_arg.md] | |
| [byte_string_arg_t][../byte_string_arg_t.md] | byte string construction tag |
| [half_arg][../half_arg.md] | |
| [half_arg_t][../half_arg_t.md] | half precision floating point number construction tag |
#include <stdexcept>
#include <string>
#include <vector>
#include <map>
#include <jsoncons/json.hpp>
using namespace jsoncons;
int main()
{
json j1; // An empty object
std::cout << "(1) " << j1 << std::endl;
json j2(json_object_arg, {{"baz", "qux"}, {"foo", "bar"}}); // An object
std::cout << "(2) " << j2 << std::endl;
json j3(json_array_arg, {"bar", "baz"}); // An array
std::cout << "(3) " << j3 << std::endl;
json j4(json::null()); // A null value
std::cout << "(4) " << j4 << std::endl;
json j5(true); // A boolean value
std::cout << "(5) " << j5 << std::endl;
double x = 1.0/7.0;
json j6(x); // A double value
std::cout << "(6) " << j6 << std::endl;
json j8("Hello"); // A text string
std::cout << "(8) " << j8 << std::endl;
std::vector<int> v = {10,20,30};
json j9 = v; // From a sequence container
std::cout << "(9) " << j9 << std::endl;
std::map<std::string, int> m{ {"one", 1}, {"two", 2}, {"three", 3} };
json j10 = m; // From an associative container
std::cout << "(10) " << j10 << std::endl;
std::vector<uint8_t> bytes = {'H','e','l','l','o'};
json j11(byte_string_arg, bytes); // A byte string
std::cout << "(11) " << j11 << std::endl;
json j12(half_arg, 0x3bff);
std::cout << "(12) " << j12.as_double() << std::endl;
}Output:
(1) {}
(2) {"baz":"qux","foo":"bar"}
(3) ["bar","baz"]
(4) null
(5) true
(6) 0.14285714285714285
(8) "Hello"
(9) [10,20,30]
(10) {"one":1,"three":3,"two":2}
(11) "SGVsbG8"
(12) 0.999512
#include <jsoncons/json.hpp>
#include <iostream>
int main()
{
std::string input = R"(
{
"machines": [
{"id": 1, "state": "running"},
{"id": 2, "state": "stopped"},
{"id": 3, "state": "running"}
]
}
)";
json j = json::parse(input);
json j_v(json_array_arg);
for (const auto& item : j.at("machines").array_range())
{
if (item.at("state").as<std::string>() == "running")
{
j_v.emplace_back(json_const_pointer_arg, &item);
}
}
std::cout << "\n(1)\n" << pretty_print(j_v) << "\n\n";
for (const auto& item : j_v.array_range())
{
std::cout << "json type: " << item.type() << ", storage kind: " << item.storage() << "\n";
}
json j2 = deep_copy(j_v);
std::cout << "\n(2)\n" << pretty_print(j2) << "\n\n";
for (const auto& item : j2.array_range())
{
std::cout << "json type: " << item.type() << ", storage kind: " << item.storage() << "\n";
}
}
Output:
(1)
[
{
"id": 1,
"state": "running"
},
{
"id": 3,
"state": "running"
}
]
json type: object, storage kind: json const pointer
json type: object, storage kind: json const pointer
(2)
[
{
"id": 1,
"state": "running"
},
{
"id": 3,
"state": "running"
}
]
json type: object, storage kind: object
json type: object, storage kind: object