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>

std::istream& operator<< ( basic_json &  j, std::istream &  i  )

friend

Deserializes an input stream to a JSON value.

Parameters

[in,out]	i	input stream to read a serialized JSON value from
[in,out]	j	JSON value to write the deserialized input to

Exceptions

std::invalid_argument

in case of parse errors

Complexity

Linear in the length of the input. The parser is a predictive LL(1) parser.

Example

The example below shows how a JSON value is constructed by reading a serialization from a stream.

#include <json.hpp>

using namespace nlohmann;

int main()
{
    // create stream with serialized JSON
    std::stringstream ss;
    ss << R"({
        "number": 23,
        "string": "Hello, world!",
        "array": [1, 2, 3, 4, 5],
        "boolean": false,
        "null": null
    })";

    // create JSON value and read the serialization from the stream
    json j;
    j << ss;

    // serialize JSON
    std::cout << std::setw(2) << j << '\n';
}

Output:

{
  "array": [
    1,
    2,
    3,
    4,
    5
  ],
  "boolean": false,
  "null": null,
  "number": 23,
  "string": "Hello, world!"
}

The example code above can be translated with

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

.

See also

parse(std::istream&, parser_callback_t) for a variant with a parser callback function to filter values while parsing