json/doc/mkdocs/docs/api/basic_json/patch.md

nlohmann::basic_json::patch

basic_json patch(const basic_json& json_patch) const;

JSON Patch 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 if the JSON patch does not consist of an array of objects.
• Throws parse_error.105 if the JSON patch is malformed (e.g., mandatory attributes are missing); example: "operation add must have member path".
• Throws out_of_range.401 if an array index is out of range.
• Throws out_of_range.403 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 if JSON pointer has no parent ("add", "remove", "move")
• Throws out_of_range.501 if "test" operation was unsuccessful.

Complexity

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 affected by the patch, 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)
• RFC 6901 (JSON Pointer)
• merge_patch applies a JSON Merge Patch

Version history

• Added in version 2.0.0.