JSON for Modern C++  3.0
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
[in]indentif 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.
1 #include <json.hpp>
2 
3 using namespace nlohmann;
4 
5 int main()
6 {
7  // create JSON values
8  json j_object = {{"one", 1}, {"two", 2}};
9  json j_array = {1, 2, 4, 8, 16};
10 
11  // call dump()
12  std::cout << j_object.dump() << "\n\n";
13  std::cout << j_object.dump(-1) << "\n\n";
14  std::cout << j_object.dump(0) << "\n\n";
15  std::cout << j_object.dump(4) << "\n\n";
16  std::cout << j_array.dump() << "\n\n";
17  std::cout << j_array.dump(-1) << "\n\n";
18  std::cout << j_array.dump(0) << "\n\n";
19  std::cout << j_array.dump(4) << "\n\n";
20 }
a class to store JSON values
Definition: json.hpp:124
string_t dump(const int indent=-1) const noexcept
serialization
Definition: json.hpp:1423
namespace for Niels Lohmann
Definition: json.hpp:59
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