Module lemmy_apub_lib::values

The enums here serve to limit a json string value to a single, hardcoded value which can be verified at compilation time. When using it as the type of a struct field, the struct can only be constructed or deserialized if the field has the exact same value.

If we used String as the field type, any value would be accepted, and we would have to check manually at runtime that it contains the expected value.

The enums in [activitystreams::activity::kind] work in the same way, and can be used to distinguish different activity types.

In the example below, MyObject can only be constructed or deserialized if media_type is text/markdown, but not if it is text/html.

use lemmy_apub_lib::values::MediaTypeMarkdown;
use serde_json::from_str;
use serde::{Deserialize, Serialize};

#[derive(Deserialize, Serialize)]
struct MyObject {
  content: String,
  media_type: MediaTypeMarkdown,
}

let markdown_json = r#"{"content": "**test**", "media_type": "text/markdown"}"#;
let from_markdown = from_str::<MyObject>(markdown_json);
assert!(from_markdown.is_ok());

let markdown_html = r#"{"content": "<b>test</b>", "media_type": "text/html"}"#;
let from_html = from_str::<MyObject>(markdown_html);
assert!(from_html.is_err());

Enums

MediaTypeHtml

Media type for HTML text/

MediaTypeMarkdown

Media type for markdown text.