Flutter Bloc Sorting event queue by a value of the event with transformEvents

Issue

Is there an easy way to sort the event queue of a flutter bloc by a value of the event class?
E.g. I have a class MyEvent with a int property and the event queue looks like this:

[MyEvent(5), MyEvent(3), MyEvent(7), AnotherEvent(), MyEvent(2), MyEvent(1)]

I want to transform the event queue/stream so that the event with the lowest int property is executed first -> [MyEvent(3), MyEvent(5), MyEvent(7), AnotherEvent(), MyEvent(1), MyEvent(2)]

It should be possible by overriding transformEvents somehow and maybe using an extension of rxdart, but I wasn’t able to get it right and would be glad if somebody could help me out. Thanks in advance!

Solution

Thanks to @narcodico, he posted this answer to my question on the flutter bloc github https://github.com/felangel/bloc/issues/2441

  @override
  Stream<Transition<SortEvent, SortState>> transformEvents(
    Stream<SortEvent> events,
    transitionFn,
  ) {
    return events
        .bufferTest((event) => event is BreakEvent)
        .flatMap<SortEvent>((bufferedEvents) async* {
      final sortedEvents = bufferedEvents.whereType<ValueEvent>().toList()
        ..sort((x, y) => x.value.compareTo(y.value));
      yield* Stream<SortEvent>.fromIterable([
        ...sortedEvents,
        ...bufferedEvents.whereType<BreakEvent>(),
      ]);
    }).asyncExpand(transitionFn);
  }

Answered By – Jeppi

Answer Checked By – Timothy Miller (FlutterFixes Admin)

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