dart - 延伸 future

Question

我发现很多关于使用而不是关于定义 future 在 Dart 。假设我有 letsWait()这需要相当长的时间。如何使用 Future类(class)？

import 'dart:async';

void main() {
  print('Let\'s get started');
  ArtificialWait waitPoint = new ArtificialWait();
  Future<String> future = waitPoint.letsWait();
  // and how about printing the return here?
  print('something fast');
}

class ArtificialWait extends Future<String> {
  String letsWait() {
    for (var i = 0; i < 5000000000; i++) {
      // lol
    }
    return 'finally';
  }
}

这次尝试给了我一个:
unresolved implicit call to super constructor 'Future()' class ArtificialWait extends Future<String> {

Answer 1

我不知道你为什么要从 Future 继承。
通常你会这样使用:

import 'dart:async';

void main() {
  print('Let\'s get started');
  artificialWait().then((e) => print(e));
  // and how about printing the return here?
  print('something fast');
}

Future<String> artificialWait  () {
  var completer = new Completer<String>();
  Timer.run(() {
    for (var i = 0; i < 5000000000; i++) {
      // lol
    }
    completer.complete('finally');
  });
  return completer.future;
}