json/api/json_editable_document.md

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 of the default json specialization: in addition to everything json_document offers, set and push_back change values after parsing, without ever rewriting the source text -- see Edits and 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`](json.md) value cannot do.

```cpp
#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:

```json
{"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 - a view of a value of a json_editable_document
• json_document - the read-only document this type adds edits to
• ordered_json_editable_document - the corresponding editable document for ordered_json
• Edits - what an edit guarantees

Version history

Since version 3.13.0.