69 lines
3.0 KiB
Markdown
69 lines
3.0 KiB
Markdown
# 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.
|