63 lines
1.8 KiB
Markdown
63 lines
1.8 KiB
Markdown
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# operator<<(basic_json)
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```cpp
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std::ostream& operator<<(std::ostream& o, const basic_json& j);
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```
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Serialize the given JSON value `j` to the output stream `o`. The JSON value will be serialized using the
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[`dump`](dump.md) member function.
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- The indentation of the output can be controlled with the member variable `width` of the output stream `o`. For
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instance, using the manipulator `std::setw(4)` on `o` sets the indentation level to `4` and the serialization result
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is the same as calling `dump(4)`.
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- The indentation character can be controlled with the member variable `fill` of the output stream `o`. For instance,
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the manipulator `std::setfill('\\t')` sets indentation to use a tab character rather than the default space character.
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## Parameters
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`o` (in, out)
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: stream to serialize to
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`j` (in)
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: JSON value to serialize
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## Return value
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the stream `o`
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## Exceptions
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Throws [`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) if a string stored inside the JSON value
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is not UTF-8 encoded. Note that unlike the [`dump`](dump.md) member functions, no `error_handler` can be set.
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## Complexity
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Linear.
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## Examples
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??? example
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The example below shows the serialization with different parameters to `width` to adjust the indentation level.
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```cpp
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--8<-- "examples/operator_serialize.cpp"
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```
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Output:
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```json
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--8<-- "examples/operator_serialize.output"
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```
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## Version history
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- Added in version 1.0.0
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- Support for indentation character added in version 3.0.0.
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!!! warning "Deprecation"
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This function replaces function `#!cpp std::ostream& operator>>(const basic_json& j, std::ostream& o)` which has
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been deprecated in version 3.0.0. It will be removed in version 4.0.0. Please replace calls like `#!cpp j >> o;`
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with `#!cpp o << j;`.
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