json.md

jsoncons::json

#include <jsoncons/json.hpp>

typedef basic_json<char,
                   Policy = sorted_policy,
                   Allocator = std::allocator<char>> json

The class json is an instantiation of the basic_json class template that uses char as the character type. The order of an object's name/value pairs is not preserved, they are sorted alphabetically by name. If you want to preserve the original insertion order, use ojson instead.

See also

ojson constructs a utf8 character json value that preserves the original insertion order of an object's name/value pairs

wjson constructs a wide character json value that sorts name-value members alphabetically

wojson constructs a wide character json value that preserves the original insertion order of an object's name/value pairs

Examples

Accessors and defaults

json j;

j["field1"] = 1;
j["field3"] = "Toronto";

double x1 = obj.contains("field1") ? j["field1"].as<double>() : 10.0;
double x2 = obj.contains("field2") ? j["field2"].as<double>() : 20.0;

std::string x3 = obj.get_value_or<std::string>("field3","Montreal");
std::string x4 = obj.get_value_or<std::string>("field4","San Francisco");

std::cout << "x1=" << x1 << '\n';
std::cout << "x2=" << x2 << '\n';
std::cout << "x3=" << x3 << '\n';
std::cout << "x4=" << x4 << '\n';

Output:

x1=1
x2=20
x3=Toronto
x4=San Francisco

Nulls

json j;
j["field1"] = json::null();
std::cout << j << '\n';

Output:

{"field1":null}

Constructing json structures

json doc;

doc["persons"] = json(json_array_arg);

json person;
person["first_name"] = "John";
person["last_name"] = "Smith";
person["birth_date"] = "1972-01-30";

json address;
address["city"] = "Toronto";
address["country"] = "Canada";

person["address"] = std::move(address);

doc["persons"].push_back(std::move(person));

std::cout << pretty_print(doc) << '\n';

Output:

{
    "persons":
    [
        {
            "address":
            {
                "city":"Toronto",
                "country":"Canada"
            },
            "birth_date":"1972-01-30",
            "first_name":"John",
            "last_name":"Smith"
        }
    ]
}