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>

string_t nlohmann::basic_json::dump ( const int  indent = -1 ) const

inlinenoexcept

Serialization function for JSON values. The function tries to mimick Python's json.dumps() function, and currently supports its indent parameter.

Parameters

indent

if indent is nonnegative, then array elements and object members will be pretty-printed with that indent level. An indent level of 0 will only insert newlines. -1 (the default) selects the most compact representation

Returns

string containing the serialization of the JSON value

Complexity

Linear.

Example

The following example shows the effect of different indent parameters to the result of the serializaion.

#include <json.hpp>

using namespace nlohmann;

int main()
{
    // create JSON values
    json j_object = {{"one", 1}, {"two", 2}};
    json j_array = {1, 2, 4, 8, 16};

    // call dump()
    std::cout << j_object.dump() << "\n\n";
    std::cout << j_object.dump(-1) << "\n\n";
    std::cout << j_object.dump(0) << "\n\n";
    std::cout << j_object.dump(4) << "\n\n";
    std::cout << j_array.dump() << "\n\n";
    std::cout << j_array.dump(-1) << "\n\n";
    std::cout << j_array.dump(0) << "\n\n";
    std::cout << j_array.dump(4) << "\n\n";
}

Output:

{"one":1,"two":2}

{"one":1,"two":2}

{
"one": 1,
"two": 2
}

{
    "one": 1,
    "two": 2
}

[1,2,4,8,16]

[1,2,4,8,16]

[
1,
2,
4,
8,
16
]

[
    1,
    2,
    4,
    8,
    16
]

The example code above can be translated with

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

.

See also

https://docs.python.org/2/library/json.html#json.dump