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Niels Lohmann
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basic_json_document gets a second template parameter, Editable (false by default), plus the aliases json_editable_document, json_editable_view, ordered_json_editable_document and ordered_json_editable_view. Editable documents can change values and structure without rewriting the source text: set()/push_back() on values, keys, array indices and JSON pointers; insert() before an array element; erase() of an object key, array index or JSON pointer. New values and element sequences go into edit storage that the document owns and never moves, so views keep referring to their value across edits and a parsed node never moves. Read-only documents walk the plain node array and are unaffected. Strings are checked for UTF-8 on entry, so dump() of an editable document never throws type_error.316. Binary values cannot be stored (type_error.319). A seeded differential test applies random edits to an editable document and to the equivalent ordered_json and compares both after every step. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
44 lines
1.5 KiB
Markdown
44 lines
1.5 KiB
Markdown
# <small>nlohmann::</small>json_editable_document
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<small>Defined in header `<nlohmann/json_view.hpp>`</small>
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```cpp
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using json_editable_document = basic_json_document<json, true>;
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```
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This type is an **editable** [`basic_json_document`](basic_json_document/index.md) of the default
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[`json`](json.md) specialization: in addition to everything [`json_document`](json_document.md) offers,
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[`set`](basic_json_document/set.md) and [`push_back`](basic_json_document/push_back.md) change values after
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parsing, without ever rewriting the source text -- see [Edits](basic_json_document/index.md#edits) and
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[Editing a document](../features/json_view.md#editing-a-document).
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## Examples
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??? example
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The example below patches two fields of a small configuration document -- changing one and adding another --
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and dumps it back out with the member order and the spelling of the untouched number preserved, something a
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plain [`json`](json.md) value cannot do.
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```cpp
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--8<-- "examples/json_editable_document.cpp"
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```
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Output:
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```json
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--8<-- "examples/json_editable_document.output"
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```
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## See also
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- [json_editable_view](json_editable_view.md) - a view of a value of a `json_editable_document`
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- [json_document](json_document.md) - the read-only document this type adds edits to
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- [ordered_json_editable_document](ordered_json_editable_document.md) - the corresponding editable document for
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`ordered_json`
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- [Edits](basic_json_document/index.md#edits) - what an edit guarantees
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## Version history
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Since version 3.13.0.
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