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Niels Lohmann
ccc005c012
- Discarded values: the legacy macro only changes <= and >=; != is true by default - Out-of-range numbers are rejected while parsing, not stored as NaN - merge_diff round trip: point to the ordered_json caveat - ensure_ascii example shows the escaped output - out_of_range.405 is thrown for "remove"/"move" on the root, not "add" - CBOR stores binary subtypes as tags - Integer/float comparison uses exact values, not conversion - diff, flatten, and the binary writers are depth-bounded - FAQ: max_digits10 for serialization, trailing commas are supported - out_of_range.407 is still thrown by to_bon8 - FetchContent_MakeAvailable needs CMake 3.14 - json_fwd.hpp contents, operator< link, RFC 7396 for merge patch - README: dump() wording, merge_diff, MSYS2/build2, patch comment typos, operator[] link, embedded CMake example aligned with the docs Signed-off-by: Niels Lohmann <mail@nlohmann.me>
43 lines
1.9 KiB
Markdown
43 lines
1.9 KiB
Markdown
# JSON Merge Patch
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The library supports JSON Merge Patch ([RFC 7396](https://tools.ietf.org/html/rfc7396)) as a patch format.
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The merge patch format is primarily intended for use with the HTTP PATCH method as a means of describing a set of
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modifications to a target resource's content. This function applies a merge patch to the current JSON value.
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Instead of using [JSON Pointer](json_pointer.md) to specify values to be manipulated, it describes the changes using a
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syntax that closely mimics the document being modified. Unlike [JSON Patch](json_patch.md), a JSON Merge Patch cannot
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express every kind of change (e.g., it cannot reorder array elements or remove a specific array element), but it is
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easier to read and write for object-shaped documents.
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The function [`merge_diff`](../api/basic_json/merge_diff.md) creates a merge patch that changes one JSON value into
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another.
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!!! tip "Not a general deep merge"
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A merge patch is not a general deep merge: a `#!json null` value in the patch deletes the key from the target.
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To merge two objects recursively (e.g., defaults and user settings), use
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[`update`](../api/basic_json/update.md) with `merge_objects` set to `#!cpp true`; see
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[Merging objects](modifying_values.md#merging-objects).
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??? example
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The following code shows how a JSON Merge Patch is applied to a JSON document.
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```cpp
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--8<-- "examples/merge_patch.cpp"
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```
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Output:
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```json
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--8<-- "examples/merge_patch.output"
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```
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## See also
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- [JSON Patch and Diff](json_patch.md) - a more expressive alternative that describes a sequence of operations
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- [JSON Pointer](json_pointer.md) - the addressing scheme used by JSON Patch
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- Function [`merge_patch`](../api/basic_json/merge_patch.md)
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- Function [`merge_diff`](../api/basic_json/merge_diff.md)
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- Function [`update`](../api/basic_json/update.md) - merge objects, optionally recursively
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