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51 lines
1.1 KiB
Markdown
51 lines
1.1 KiB
Markdown
# <small>nlohmann::basic_json::</small>flatten
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```cpp
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basic_json flatten() const;
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```
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The function creates a JSON object whose keys are JSON pointers (see [RFC 6901](https://tools.ietf.org/html/rfc6901))
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and whose values are all primitive (see [`is_primitive()`](is_primitive.md) for more information). The original JSON
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value can be restored using the [`unflatten()`](unflatten.md) function.
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## Return value
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an object that maps JSON pointers to primitive values
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## Exception safety
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Strong exception safety: if an exception occurs, the original value stays intact.
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## Complexity
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Linear in the size the JSON value.
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## Notes
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Empty objects and arrays are flattened to `#!json null` and will not be reconstructed correctly by the
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[`unflatten()`](unflatten.md) function.
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## Examples
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??? example
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The following code shows how a JSON object is flattened to an object whose keys consist of JSON pointers.
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```cpp
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--8<-- "examples/flatten.cpp"
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```
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Output:
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```json
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--8<-- "examples/flatten.output"
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```
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## See also
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- [unflatten](unflatten.md) the reverse function
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## Version history
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- Added in version 2.0.0.
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