Question

我希望,用户能够花一个时间回击,能够取消。与此类似:

def main: F[Unit] =
  for
    cancel       <- runTimer(callback, 5.seconds)
    shouldCancel <- askUser
    _            <- cancel.whenA(shouldCancel)
  yield ()

我怎么能以FS2的类别来做?

Answer 1

由于cats-effect在解决一致问题时具有非常强的威力,你需要的守则实际上非常简单:

def runTimer(
  callback: IO[Unit],
  delay: Duration,
  cancel: IO[Unit]
): IO[Unit] =
  IO.race(
    IO.sleep(delay) >> callback.uncancelable,
    cancel
  ).void

主要方面如下:

Using IO.sleep to delay the execution of the callback.
Using uncancelable to make the callback uncancelable.
Using IO.race to run both the delayed callback and the cancel concurrently. If the cancel completes before the delay, the race will cancel the execution of the callback.

您可以改进这项工作,以确保<代码>cancel>可取消<编码> 查询背书/代码>,但允许在上一级取消整个<代码><<>race>/code>。

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