我如何在.forEach互动中暂停一下 [英] How would I put a pause in a .forEach interation

问题描述

我正试图在forEach循环之间添加一个暂停列表.

I am attempting to put in a pause between a forEach loop for a list.

我本以为超时会导致循环暂停，但似乎一次只能启动3个计时器. (非常连续).

I would have thought the timeout would cause a pause for the loop but it just seems to start 3 timers all at once. (In very quick succession.)

  startTimeout(int seconds) async {
    print('Timer Being called now');
    var duration = Duration(seconds: seconds);
    Timer(duration, doSomething());
  }


  startDelayedWordPrint() {
    List<String> testList = ['sfs','sdfsdf', 'sfdsf'];
    testList.forEach((value) async {
      await startTimeout(30000);
      print('Writing another word $value');
    });
  }

知道我该怎么做吗?

Any idea how I might do this?

推荐答案

使用await Future.delayed()暂停一定的持续时间并进行for循环，而不是forEach()

Use await Future.delayed() to pause for certain duration and a for loop, instead of forEach()

如果forEach()接收异步函数，则每个迭代调用将在单独的异步上下文中运行，其原因类似于并行代码执行.同时forEach它自己将立即返回，而无需等待任何异步功能完成.

If forEach() receives async functions, each iteration call will run in a separate asynchronous context which can be reasoned about similarly to parallel code execution. Meanwhile forEach it self will return immediately without waiting until any async function to complete.

在List.forEach()中进行异步/等待

样本: https://dartpad.dartlang.org/a57a500d4593aebe1bad0ed79376016c

main() async {
    List<String> testList = ['sfs','sdfsdf', 'sfdsf'];
    for(final value in testList) {
      await Future.delayed(Duration(seconds: 1));
      print('Writing another word $value');
    };
  }

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