gistfile1.txt

import 'dart:async';

final streamController = StreamController<int>();

Future<void> process(int event) async {
  print("Processing $event...");
}

Stream<String> mapEventToState(int event) async* {
  yield "Loading $event...";
  await process(event);
  yield "Loaded $event";
  if (event == 0) {
    send(4);
  }
}

void send(int event) {
  streamController.add(event); 
  print("Sent $event");
}

void main() {
  streamController.stream.asyncExpand((event) => mapEventToState(event)).listen((state) => print("State: $state"));
  for (int i = 0; i < 3; i++) {
    send(i);
  }
}