Streams, ordering, and cancellation

The idea

A Future represents one eventual outcome, while a Stream represents asynchronous events over time. Await for processes events sequentially and can use ordinary try and catch around the consumption loop. A stream may emit errors as well as data. Decide whether a failure should stop processing, be reported, or be transformed instead of treating every stream like a finite list.

A single-subscription stream and a broadcast stream have different listener contracts. Broadcast delivery does not automatically replay old events to late listeners. Cancellation should release resources owned by a producer or subscription, but it does not undo work already completed. Keep event ordering and buffering assumptions explicit, especially when adding asynchronous transformations or connecting a fast producer to a slower consumer.

Stream<int> counts() async* { yield 2; yield 5; }
Future<void> main() async {
  var total=0;
  await for (final n in counts()) { total+=n; }
  print(total);
}

7

The loop waits for both ordered events and prints the aggregate after the stream completes.