Stream yield async

main.dart

import 'dart:async';

void main() async {
  Future<int> computeCost(int val) async {
    await Future.delayed(Duration(seconds: 1));
    return val * 2;
  }

  Stream<int> generateValues1() {
    return Stream.periodic(Duration(seconds: 1), (val) {
      return val;
    });
  }

  Stream<int> generateValues2() {
    return Stream.periodic(Duration(seconds: 1), (val) {
      return computeCost(val);
    }).map((futureRes) {
      futureRes.then((val) => print("Test: $val"));
    });
  }

  Stream<int> generateValues3() async* {
    int i = 0;
    while (true) {
      await Future.delayed(Duration(seconds: 1));
      yield i++;
    }
  }

  Stream<int> generateValues4() async* {
    int i = 0;
    while (true) {
      await Future.delayed(Duration(seconds: 2));
      final cost = await computeCost(i++);
      yield cost;
    }
  }

  Stream<int> generateValues5() async* {
    yield* generateValues3();
  }

  final subscription=generateValues5().listen((val) => print(val));
  
  await Future.delayed(Duration(seconds: 10));
  print("Cancelling subscription");
  subscription.cancel();
  
}