Flutter How to make Stream complete before executing the next operation-CodePudding

code:

import 'dart:async';

void main() {
  StreamController<int> controller = StreamController();
  StreamSubscription streamSubscription =
      controller.stream.listen((event) async {
    await f(event);
  });

  controller.add(5);
  controller.add(3);
  controller.add(1);
}

Future<void> f(int duration) async {
  await Future.delayed(Duration(seconds: duration));
  print('$duration');
}

output: 1 3 5

the result i want: 5 3 1 How can I modify the code, or what other api to use

CodePudding user response：

Just remove your delay function and use the following:

import 'dart:async';

void main() {
  StreamController<int> controller = StreamController();
  StreamSubscription streamSubscription =
      controller.stream.listen(
  (event) => print('Event: $event'),
  onDone: () => print('Done'),
  one rror: (error) => print(error),
);

  controller.add(5);
  controller.add(3);
  controller.add(1);
  
  
}

CodePudding user response：

Don't use streams?

Why are you using streams if you want to ruin the point of using them.

void main() async {
  await f(5);
  await f(3);
  await f(1);
}

Future<void> f(int duration) async {
  await Future.delayed(Duration(seconds: duration));
  print('$duration');
}

output: 5 3 1 with delay 5s, 3s, 1s as you wanted