# nlohmann::basic_json::patch
```cpp
basic_json patch(const basic_json& json_patch) const;
```
[JSON Patch](http://jsonpatch.com) defines a JSON document structure for expressing a sequence of operations to apply to
a JSON document. With this function, a JSON Patch is applied to the current JSON value by executing all operations from
the patch.
## Parameters
`json_patch` (in)
: JSON patch document
## Return value
patched document
## Exception safety
Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
## Exceptions
- Throws [`parse_error.104`](../../home/exceptions.md#jsonexceptionparse_error104) if the JSON patch does not consist of
an array of objects.
- Throws [`parse_error.105`](../../home/exceptions.md#jsonexceptionparse_error105) if the JSON patch is malformed (e.g.,
mandatory attributes are missing); example: `"operation add must have member path"`.
- Throws [`out_of_range.401`](../../home/exceptions.md#jsonexceptionout_of_range401) if an array index is out of range.
- Throws [`out_of_range.403`](../../home/exceptions.md#jsonexceptionout_of_range403) if a JSON pointer inside the patch
could not be resolved successfully in the current JSON value; example: `"key baz not found"`.
- Throws [`out_of_range.405`](../../home/exceptions.md#jsonexceptionout_of_range405) if JSON pointer has no parent
("add", "remove", "move")
- Throws [`out_of_range.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
unsuccessful.
## Complexity
Linear in the size of the JSON value and the length of the JSON patch. As usually the patch affects only a fraction of
the JSON value, the complexity can usually be neglected.
## Notes
The application of a patch is atomic: Either all operations succeed and the patched document is returned or an exception
is thrown. In any case, the original value is not changed: the patch is applied to a copy of the value.
## Examples
??? example
The following code shows how a JSON patch is applied to a value.
```cpp
--8<-- "examples/patch.cpp"
```
Output:
```json
--8<-- "examples/patch.output"
```
## See also
- [RFC 6902 (JSON Patch)](https://tools.ietf.org/html/rfc6902)
- [RFC 6901 (JSON Pointer)](https://tools.ietf.org/html/rfc6901)
- [patch_inplace](patch_inplace.md) applies a JSON Patch without creating a copy of the document
- [merge_patch](merge_patch.md) applies a JSON Merge Patch
## Version history
- Added in version 2.0.0.
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