JSON for Modern C++ 2.1.1
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◆ operator<< [1/2]

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 = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer>
std::istream & operator<< ( basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer > &  j,
std::istream &  i 
)
friend

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\n Linear in the length of the input. The parser is a predictive
LL(1) parser.
Note
A UTF-8 byte order mark is silently ignored.
Example\n The example below shows how a JSON value is constructed by
reading a serialization from a stream.
1#include <json.hpp>
2
3using json = nlohmann::json;
4
5int 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}
static basic_json array(std::initializer_list< basic_json > init=std::initializer_list< basic_json >())
explicitly create an array from an initializer list
Definition json.hpp:2165
a class to store JSON values
Definition json.hpp:1040
basic_json<> json
default JSON class
Definition json.hpp:12369

Output (play with this example online):
{
  "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&, const parser_callback_t) for a variant with a parser callback function to filter values while parsing
Since
version 1.0.0

Definition at line 6514 of file json.hpp.