template<template< typename U, typename V, typename...Args > class ObjectType = std::map, template< typename U, typename...Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = int64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>

template<class CompatibleObjectType , typename std::enable_if< std::is_constructible< typename object_t::key_type, typename CompatibleObjectType::key_type >::value andstd::is_constructible< basic_json, typename CompatibleObjectType::mapped_type >::value, int >::type = 0>

nlohmann::basic_json::basic_json ( const CompatibleObjectType &  value )

inline

Create an object JSON value with a given content. This constructor allows any type that can be used to construct values of type object_t. Examples include the types std::map and std::unordered_map.

Template Parameters

CompatibleObjectType

an object type whose key_type and value_type is compatible to object_t

Parameters

[in]

value

a value for the object

Complexity

Linear in the size of the passed value.

Exceptions

std::bad_alloc

if allocation for object value fails (thrown by the constructor of json_value)

Example

The following code shows the constructor with several compatible object type parameters.

#include <json.hpp>
#include <unordered_map>

using namespace nlohmann;

int main()
{
    // create an object from std::map
    std::map<std::string, int> c_map
    {
        {"one", 1}, {"two", 2}, {"three", 3}
    };
    json j_map(c_map);

    // create an object from std::unordered_map
    std::unordered_map<const char*, double> c_umap
    {
        {"one", 1.2}, {"two", 2.3}, {"three", 3.4}
    };
    json j_umap(c_umap);

    // create an object from std::multimap
    std::multimap<std::string, bool> c_mmap
    {
        {"one", true}, {"two", true}, {"three", false}, {"three", true}
    };
    json j_mmap(c_mmap); // only one entry for key "three" is used

    // create an object from std::unordered_multimap
    std::unordered_multimap<std::string, bool> c_ummap
    {
        {"one", true}, {"two", true}, {"three", false}, {"three", true}
    };
    json j_ummap(c_ummap); // only one entry for key "three" is used

    // serialize the JSON objects
    std::cout << j_map << '\n';
    std::cout << j_umap << '\n';
    std::cout << j_mmap << '\n';
    std::cout << j_ummap << '\n';
}

Output:

{"one":1,"three":3,"two":2}
{"one":1.2,"three":3.4,"two":2.3}
{"one":true,"three":false,"two":true}
{"one":true,"three":false,"two":true}

The example code above can be translated with

g++ -std=c++11 -Isrc doc/examples/basic_json__CompatibleObjectType.cpp -o basic_json__CompatibleObjectType 

.

See also

basic_json(const object_t&)