Trait StateField

Source

pub trait StateField:
    Send
    + Sync
    + Debug {
    type Value: Resource;

    // Required methods
    fn init<'life0, 'life1, 'life2, 'async_trait>(
        &'life0 self,
        config: &'life1 StateConfig,
        instance: &'life2 State,
    ) -> Pin<Box<dyn Future<Output = Arc<Self::Value>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait,
             'life1: 'async_trait,
             'life2: 'async_trait;
    fn apply<'life0, 'life1, 'life2, 'life3, 'async_trait>(
        &'life0 self,
        tr: &'life1 Transaction,
        value: Arc<Self::Value>,
        old_state: &'life2 State,
        new_state: &'life3 State,
    ) -> Pin<Box<dyn Future<Output = Arc<Self::Value>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait,
             'life1: 'async_trait,
             'life2: 'async_trait,
             'life3: 'async_trait;

    // Provided methods
    fn serialize(&self, _value: &Arc<Self::Value>) -> Option<Vec<u8>> { ... }
    fn deserialize(&self, _data: &[u8]) -> Option<Arc<Self::Value>> { ... }
}

Expand description

PluginTrait实现一个 default 实现状态字段特征使用关联类型保持类型信息，提供类型安全的插件状态管理

§优势

✅ 编译期类型检查，无需运行时 downcast
✅ 更好的性能和代码可读性
✅ IDE 支持更好的自动补全

§示例

#[derive(Debug)]
struct MyValue {
    count: u32,
}
impl Resource for MyValue {}

#[derive(Debug)]
struct MyStateField;

#[async_trait]
impl StateField for MyStateField {
    type Value = MyValue;

    async fn init(&self, _config: &StateConfig, _state: &State) -> Arc<MyValue> {
        Arc::new(MyValue { count: 0 })
    }

    async fn apply(&self, _tr: &Transaction, value: Arc<MyValue>,
                  _old: &State, _new: &State) -> Arc<MyValue> {
        // ✅ 类型安全，无需 downcast
        Arc::new(MyValue { count: value.count + 1 })
    }
}