nlohmann::operator>>(basic_json)

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

Deserializes an input stream to a JSON value.

Parameters

i (in, out): input stream to read a serialized JSON value from
j (in, out): JSON value to write the deserialized input to

Return value

the stream i

Exceptions

Throws parse_error.101 in case of an unexpected token.

Complexity

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

Notes

A UTF-8 byte order mark is silently ignored.

Invalid Unicode escapes and unpaired surrogates in the input are reported as parse_error.101 with a detailed message.

operator>> parses exactly one JSON value and leaves the stream positioned right after it, so it can be called repeatedly to read a sequence of concatenated JSON values from the same stream:

json j1, j2;
input >> j1;  // parses the first value, stream now positioned right after it
input >> j2;  // parses the next value

Note this does not work for JSON Lines (newline-delimited JSON) input -- see that page for why and for the recommended alternative.

!!! warning "Deprecation"

This function replaces function `#!cpp std::istream& operator<<(basic_json& j, std::istream& i)` which has
been deprecated in version 3.0.0. It will be removed in version 4.0.0. Please replace calls like `#!cpp j << i;`
with `#!cpp i >> j;`.

Examples

??? example

The example below shows how a JSON value is constructed by reading a serialization from a stream.
    
```cpp
--8<-- "examples/operator_deserialize.cpp"
```

Output:

```json
--8<-- "examples/operator_deserialize.output"
```

Version history

Added in version 1.0.0.

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