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>
std::istream& operator>> ( std::istream &  i,
basic_json j 
)
friend

deserialize from stream Deserializes an input stream to a JSON value.

Parameters
[in,out]iinput stream to read a serialized JSON value from
[in,out]jJSON value to write the deserialized input to
Exceptions
std::invalid_argumentin 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.
1 #include <json.hpp>
2 
3 using namespace nlohmann;
4 
5 int main()
6 {
7  // create stream with serialized JSON
8  std::stringstream ss;
9  ss << R"({
10  "number": 23,
11  "string": "Hello, world!",
12  "array": [1, 2, 3, 4, 5],
13  "boolean": false,
14  "null": null
15  })";
16 
17  // create JSON value and read the serialization from the stream
18  json j;
19  j << ss;
20 
21  // serialize JSON
22  std::cout << std::setw(2) << j << '\n';
23 }
a class to store JSON values
Definition: json.hpp:121
namespace for Niels Lohmann
Definition: json.hpp:56
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