Dart avait Future，仅推迟某行代码并执行其余代码答案

【问题标题】：Dart avait Future, postpone just certain line of code and execute the restDart avait Future，仅推迟某行代码并执行其余代码
【发布时间】：2021-11-29 18:35:57
【问题描述】：

想要推迟某些代码行，使用 await Future 并且效果很好，问题是它推迟了它之后的所有代码，我需要它推迟某些代码行，同时继续执行其余的代码立即编码

void main() async {
  for (int i = 0; i < 5; i++) {
       await Future.delayed(Duration(seconds: 1));
    //postpone just next line or few lines of code
    print('postpone this line of code ${i + 1}');
    print('postpone me too');
  }
  //should execute without being postponed
  print('continue imediately without being postponed by await Future');
}

这可以通过 await Future 或其他一些功能实现吗？

【问题讨论】：

标签： dart async-await future

【解决方案1】：

await 它是注册Future.then 回调的语法糖。使用await 的目的是更容易让所有后续代码等待Future 完成。如果这不是你想要的，你可以直接使用Future.then：

void main() {
  for (int i = 0; i < 5; i++) {
    Future.delayed(const Duration(seconds: 1)).then((_) {
      print('postpone this line of code ${i + 1}');
      print('postpone me too');
    });
  }
  print('continue immediately without being postponed by await Future');
}

由于Future.delayed有回调，你也可以完全跳过then：

void main() {
  for (int i = 0; i < 5; i++) {
    Future.delayed(const Duration(seconds: 1), () {
      print('postpone this line of code ${i + 1}');
      print('postpone me too');
    });
  }
  print('continue immediately without being postponed by await Future');
}

如果你不使用创建的未来做任何事情，这相当于使用Timer：

import 'dart:async' show Timer;
void main() {
  for (int i = 0; i < 5; i++) {
    Timer(const Duration(seconds: 1), () {
      print('postpone this line of code ${i + 1}');
      print('postpone me too');
    });
  }
  print('continue immediately without being postponed by await Future');
}

【讨论】：