* 🔥 consolidate documentation
* ♻️ overwork std specializations
* 🚚 move images files to mkdocs
* ♻️ fix URLs
* 🔧 tweak MkDocs configuration
* 🔧 add namespaces
* 📝 document deprecations
* 📝 document documentation generation
* 🚸 improve search
* 🚸 add examples
* 🚧 start adding documentation for macros
* 📝 add note for https://github.com/nlohmann/json/issues/874#issuecomment-1001699139
* 📝 overwork example handling
* 📝 fix Markdown tables

2021-12-29 13:41:01 +01:00

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operator<<(basic_json)

std::ostream& operator<<(std::ostream& o, const basic_json& j);

Serialize the given JSON value j to the output stream o. The JSON value will be serialized using the dump member function.

The indentation of the output can be controlled with the member variable width of the output stream o. For instance, using the manipulator std::setw(4) on o sets the indentation level to 4 and the serialization result is the same as calling dump(4).
The indentation character can be controlled with the member variable fill of the output stream o. For instance, the manipulator std::setfill('\\t') sets indentation to use a tab character rather than the default space character.

Parameters

o (in, out): stream to serialize to
j (in): JSON value to serialize

Return value

the stream o

Exceptions

Throws type_error.316 if a string stored inside the JSON value is not UTF-8 encoded. Note that unlike the dump member functions, no error_handler can be set.

Complexity

Linear.

Examples

??? example

The example below shows the serialization with different parameters to `width` to adjust the indentation level.
    
```cpp
--8<-- "examples/operator_serialize.cpp"
```

Output:

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

Version history

Added in version 1.0.0
Support for indentation character added in version 3.0.0.

!!! warning "Deprecation"

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

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