Bloc: debounceTime problem when pagination

[konstantin-doncov]

I want to paginate a ListView, so I use NotificationListener<ScrollNotification> which adds new event when the end of the ListView is reached. But I want to use debounce to get rid of spamming event about end of the ListView. So I use it in this way in the Bloc:

  @override
  Stream<ListState> transformEvents(
      Stream<ListEvent> events,
      Stream<ListState> Function(ListEvent event) next,
      ) {
    return super.transformEvents(
      events.debounceTime(
        Duration(milliseconds: 500),
      ),
      next,
    );
  }

But now I have three problems:

1. If I will keep scrolling down(and generate events more often than every 500 milliseconds), then nothing will happen, the event will not be received. How can I fix it?
2. Now every event class has debounceTime, how can I specify which subclasses of ListEvent should has debounceTime?
3. How can I set that debounceTime should be only between two instances of the same class? Thus, for example, if this is the first event of this class, then debounceTime isn't needed.

[felangel]

Hi @don-prog 👋
Thanks for opening an issue!

Have you checked out https://github.com/felangel/bloc/issues/524#issuecomment-573978217?

[konstantin-doncov]

@felangel thanks, I think this comment solves my second question. And what about two others?

[felangel]

1. This is how debounceTime works. Maybe you're looking for a different operator like throttle or buffer?
2. Check out https://github.com/ReactiveX/rxdart/blob/b0edb3d0b2adfb8245b6692623c2ae863c8b520c/lib/src/transformers/backpressure/debounce.dart#L61

[felangel]

Closing for now but feel free to comment with additional questions or details and I’m happy to continue the conversation 👍

[konstantin-doncov]

@felangel sorry, I forgot to reply. throttleTime is what I need, thanks!