rust - 在事件类型之间转换

Question

关于如何正确比较从frame_system::Module::events()获得的事件是否等于从当前托盘decl_event!获得的特定事件有任何线索吗？
我试图将列表中的事件与内部PostCreated事件进行匹配:

let events: Vec<EventRecord<<T as system::Trait>::Event, T::Hash>> = SystemModule::<T>::events();
        
events.iter().filter(|EventRecord { event, .. }| {
    matches!(event, RawEvent::PostCreated(_, _))
});

但是，出现了一个错误:

428 |             matches!(event, RawEvent::PostCreated(_, _))
    |                      -----  ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected associated type, found enum `RawEvent`
    |                      |
    |                      this expression has type `&<T as frame_system::Trait>::Event`
    |
    = note: expected associated type `<T as frame_system::Trait>::Event`
                          found enum `RawEvent<_>`
    = help: consider constraining the associated type `<T as frame_system::Trait>::Event` to `RawEvent<_>`

此外，如果我将.into()添加到事件中，则会收到另一个错误:

428 |             matches!(event.into(), RawEvent::PostCreated(_, _))
    |                            ^^^^ the trait `std::convert::From<&<T as frame_system::Trait>::Event>` is not implemented for `RawEvent<_>`
    |
    = note: required because of the requirements on the impl of `std::convert::Into<RawEvent<_>>` for `&<T as frame_system::Trait>::Event`

我将不胜感激。确保这几行代码确实有问题。

Answer 1

您的“一般”事件类型应在您的配置特征中定义如下:

/// The overarching event type.
type Event: From<Event<Self>> + Into<<Self as frame_system::Trait>::Event>;

这意味着我们支持托盘中定义的From枚举的Event特征，以及Into托盘中Event枚举的frame_system特征。
因此，转换可以如下:

原始事件->通用事件

通用事件->系统事件

所以:

let generic_event: <T as Trait>::Event = RawEvent::MyEvent.into();
let system_event: <T as frame_system::Trait>::Event = generic_event.into();

然后，您可以将此system_event与您从frame_system::Module::<T>::events()返回的事件进行比较。