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73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
# <small>nlohmann::basic_json::</small>patch
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```cpp
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basic_json patch(const basic_json& json_patch) const;
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```
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[JSON Patch](http://jsonpatch.com) defines a JSON document structure for expressing a sequence of operations to apply to
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a JSON document. With this function, a JSON Patch is applied to the current JSON value by executing all operations from
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the patch.
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## Parameters
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`json_patch` (in)
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: JSON patch document
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## Return value
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patched document
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## Exception safety
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Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
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## Exceptions
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- Throws [`parse_error.104`](../../home/exceptions.md#jsonexceptionparse_error104) if the JSON patch does not consist of
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an array of objects.
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- Throws [`parse_error.105`](../../home/exceptions.md#jsonexceptionparse_error105) if the JSON patch is malformed (e.g.,
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mandatory attributes are missing); example: `"operation add must have member path"`.
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- Throws [`out_of_range.401`](../../home/exceptions.md#jsonexceptionout_of_range401) if an array index is out of range.
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- Throws [`out_of_range.403`](../../home/exceptions.md#jsonexceptionout_of_range403) if a JSON pointer inside the patch
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could not be resolved successfully in the current JSON value; example: `"key baz not found"`.
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- Throws [`out_of_range.405`](../../home/exceptions.md#jsonexceptionout_of_range405) if JSON pointer has no parent
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("add", "remove", "move")
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- Throws [`out_of_range.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
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unsuccessful.
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## Complexity
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Linear in the size of the JSON value and the length of the JSON patch. As usually only a fraction of the JSON value is
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affected by the patch, the complexity can usually be neglected.
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## Notes
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The application of a patch is atomic: Either all operations succeed and the patched document is returned or an exception
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is thrown. In any case, the original value is not changed: the patch is applied to a copy of the value.
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## Examples
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??? example
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The following code shows how a JSON patch is applied to a value.
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```cpp
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--8<-- "examples/patch.cpp"
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```
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Output:
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```json
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--8<-- "examples/patch.output"
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```
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## See also
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- [RFC 6902 (JSON Patch)](https://tools.ietf.org/html/rfc6902)
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- [RFC 6901 (JSON Pointer)](https://tools.ietf.org/html/rfc6901)
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- [merge_patch](merge_patch.md) applies a JSON Merge Patch
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## Version history
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- Added in version 2.0.0.
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