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api/json_editable_document/index.md

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+# nlohmann::json_editable_document
+
+Defined in header `<nlohmann/json_view.hpp>`
+
+```
+using json_editable_document = basic_json_document<json, true>;
+```
+
+This type is an **editable** [`basic_json_document`](https://json.nlohmann.me/api/basic_json_document/index.md) of the default [`json`](https://json.nlohmann.me/api/json/index.md) specialization: in addition to everything [`json_document`](https://json.nlohmann.me/api/json_document/index.md) offers, [`set`](https://json.nlohmann.me/api/basic_json_document/set/index.md) and [`push_back`](https://json.nlohmann.me/api/basic_json_document/push_back/index.md) change values after parsing, without ever rewriting the source text -- see [Edits](https://json.nlohmann.me/api/basic_json_document/#edits) and [Editing a document](https://json.nlohmann.me/features/json_view/#editing-a-document).
+
+## Examples
+
+Example
+
+The example below patches two fields of a small configuration document -- changing one and adding another -- and dumps it back out with the member order and the spelling of the untouched number preserved, something a plain [`json`](https://json.nlohmann.me/api/json/index.md) value cannot do.
+
+```
+#include <iostream>
+#include <nlohmann/json_view.hpp>
+
+using json = nlohmann::json;
+using json_editable_document = nlohmann::json_editable_document;
+using json_editable_view = nlohmann::json_editable_view;
+
+int main()
+{
+    // a configuration file, as it might be read from disk
+    const std::string text = R"({"name": "cache", "host": "db1", "port": 6379, "price": 19.90})";
+    std::cout << text << "\n\n";
+
+    // patch two fields -- "price" is never touched
+    json_editable_document doc = json_editable_document::parse(text);
+    doc.set(doc.root(), "host", "db2");
+    doc.set(doc.root(), "retries", 3);
+
+    // member order (the new member at the end) and the untouched number's
+    // exact spelling survive
+    std::cout << doc.root().dump(-1, ' ', false, json_editable_view::number_format::source) << '\n';
+
+    // the same patch on a plain json value: keys are sorted (object_t is a
+    // std::map), and "price" is rewritten even though the patch never
+    // touched it
+    json plain = json::parse(text);
+    plain["host"] = "db2";
+    plain["retries"] = 3;
+    std::cout << plain.dump() << '\n';
+}
+```
+
+Output:
+
+```
+{"name": "cache", "host": "db1", "port": 6379, "price": 19.90}
+
+{"name":"cache","host":"db2","port":6379,"price":19.90,"retries":3}
+{"host":"db2","name":"cache","port":6379,"price":19.9,"retries":3}
+```
+
+## See also
+
+- [json_editable_view](https://json.nlohmann.me/api/json_editable_view/index.md) - a view of a value of a `json_editable_document`
+- [json_document](https://json.nlohmann.me/api/json_document/index.md) - the read-only document this type adds edits to
+- [ordered_json_editable_document](https://json.nlohmann.me/api/ordered_json_editable_document/index.md) - the corresponding editable document for `ordered_json`
+- [Edits](https://json.nlohmann.me/api/basic_json_document/#edits) - what an edit guarantees
+
+## Version history
+
+Since version 3.13.0 unreleased.