Flutter - 轉換顫振 bloc 事件以添加去抖動 (Flutter - Transform flutter bloc event to add debounce)

@override
  Stream<GithubSearchState> transformEvents(
    Stream<GithubSearchEvent> events,
    Stream<GithubSearchState> Function(GithubSearchEvent event) next,
  ) {
    return (events as Observable<GithubSearchEvent>)
        .debounceTime(
          Duration(milliseconds: 300),
        )
        .switchMap(next);
  }

我面臨的問題是 Observable 已被 RxDart 棄用，我不確定如何完成上述要求。

參考解法

方法 1:

Since bloc 8.0.0 the syntax changed and you need to pass it as a transformer to the on function. Apart from the debouncing you should think about concurrency. To combine sequential processing with a debounce, you can provide the following function:

import 'package:rxdart/rxdart.dart';
//...

    on<GithubSearchEvent>(
      (event, emit) {},
      transformer: (events, mapper) {
        return events.debounceTime(const Duration(milliseconds: 300)).asyncExpand(mapper);
      },
    );

You can create a reusable transformer as a top‑level function like this:

EventTransformer<Event> debounceSequential<Event>(Duration duration) {
  return (events, mapper) => events.debounceTime(duration).asyncExpand(mapper);
}

and use it like this:

    on<GithubSearchEvent>(
      (event, emit) {},
      transformer: debounceSequential(const Duration(milliseconds: 300)),
    );

方法 2:

I found the solution.

@override
  Stream<Transition< GithubSearchEvent, GithubSearchState >> transformEvents(
      Stream< GithubSearchEvent > events, transitionFn) {
    return events
        .debounceTime(const Duration(milliseconds: 300))
        .switchMap((transitionFn));
  }

方法 3:

I cannt add comment to @user2220771 cause my reputation is too low.

This will not work:

EventTransformer<Event> debounceTransformer<Event>(Duration duration) {
  return (events, mapper) => events.debounceTime(duration);
}

you have to switch map as:

EventTransformer<Event> debounceTransformer<Event>(Duration duration) {
  return (events, mapper) {
    return events.debounceTime(duration).switchMap(mapper);
  };
}

(by Suhas Shelar、user2220771、Suhas Shelar、Thioby)

參考文件

1. Flutter ‑ Transform flutter bloc event to add debounce (CC BY‑SA 2.5/3.0/4.0)