我怎么知道两个Streams何时完成？

Question

我正在使用Dart的Streams进行异步事件.我有两个流,我想知道两个流何时完成(也就是关闭).我想用Futures做这件事.我该怎么做？

Answer 1

A StreamSubscription可以回归未来asFuture.当流关闭时,订阅的未来完成.

使用Future.wait等待两个流期货来完成.

这是一个例子:

import 'dart:async';

Future listenOnTwoStreams(Stream s1, Stream s2) {
  StreamSubscription sub1 = s1.listen((e) => print(e));
  StreamSubscription sub2 = s2.listen((e) => print(e));

  Future f1 = sub1.asFuture();
  Future f2 = sub2.asFuture();

  return Future.wait([f1, f2]).then((e) => print("all done!"));
}

void main() {
  StreamController controller1 = new StreamController();
  StreamController controller2 = new StreamController();

  Stream s1 = controller1.stream;
  Stream s2 = controller2.stream;

  listenOnTwoStreams(s1, s2);

  Timer.run(() {
    controller1.add("1");
    controller2.add("2");

    controller1.close();
    controller2.close();
  });
}