如何重复运行一个函数，直到它返回 true 或超时？

huangapple
go评论117阅读模式
英文:

How to repetitively run a function until it returns true or timeout?

问题

我有一个名为checkSuccess()的函数，如果任务已完成，则返回true。

我想每隔1秒调用一次checkSuccess()，并在它返回true或超时时中断。

目前我使用一个goroutine来运行一个for循环，在其中每隔1秒调用一次checkSuccess()。在主进程中，我使用time.After来检查整个检查持续时间是否已超时。

  1. func myfunc(timeout time.Duration) {
  3. 	successChan := make(chan struct{})
  4. 	timeoutChan := make(chan struct{})
  6. 	// 持续监听任务
  7. 	go func() {
  8. 		for {
  9. 			select {
  10. 			// 如果已达到超时时间，则退出for循环
  11. 			case <-timeoutChan:
  12. 				return
  13. 			default:
  14. 			}
  15. 			// 如果任务已成功，则提前退出
  16. 			if checkSuccess() {
  17. 				close(successChan)
  18. 				return
  19. 			}
  20. 			time.Sleep(time.Second)
  21. 		}
  22. 	}()
  24. 	// 一旦超时，停止监听任务
  25. 	select {
  26. 	case <-time.After(timeout):
  27. 		close(timeoutChan)
  28. 		return
  29. 	case <-successChan:
  30. 		return
  31. 	}
  33. 	return
  34. }

实际上，这已经实现了我的目标，但我觉得它很繁琐。有没有更好（更短）的编写方式？

英文:

I have a function checkSuccess() which return true if the task have finished.

I'd like to call checkSuccess() every 1 second and break until it return true or timeout.

What I'm having now is to use a goroutine to run a for loop, in which I call checkSuccess() every 1 second. And in the main process, I use time.After to check if the whole checking duration has passed timeout.

  1. func myfunc (timeout time.Duration) {
  3. 	successChan := make(chan struct{})
  4. 	timeoutChan := make(chan struct{})
  6. 	// Keep listening to the task.
  7. 	go func() {
  8. 		for {
  9. 			select {
  10.             // Exit the forloop if the timeout has been reached
  11. 			case &lt;-timeoutChan:
  12. 				return
  13. 			default:
  14. 			}
  15. 			// Early exit if task has succeed.
  16. 			if checkSuccess() {
  17. 				close(successChan)
  18. 				return
  19. 			}
  20.         time.Sleep(time.Second)
  21. 		}
  22. 	}()
  24. 	// Once timeout, stop listening to the task.
  25. 	select {
  26. 	case &lt;-time.After(timeout):
  27. 		close(timeoutChan)
  28.         return 
  29. 	case &lt;-successChan:
  30. 		return
  31. 	}
  33. 	return
  34. }

It actually has achieved my goal, but I found it very tedious. Is there any better (shorter) way to write it?

答案1

得分: 6

你不需要单独的goroutine或通道：

  1. func myfunc(timeout time.Duration) {
  2.    ticker := time.NewTicker(time.Second)
  3.    defer ticker.Close()
  4.    to := time.NewTimer(timeout)
  5.    defer to.Stop()
  6.    for {
  7.       select {
  8.          case <-to.C:
  9.            return // 超时
  10.          case <-ticker.C:
  11.            if checkSuccess() {
  12.              return
  13.            }
  14.       }
  15.    }
  16. }
英文:

You don't need a separate goroutine or channels:

  1. func myfunc (timeout time.Duration) {
  2.    ticker:=time.NewTicker(time.Second)
  3.    defer ticker.Close()
  4.    to:=time.NewTimer(timeout)
  5.    defer to.Stop()
  6.    for {
  7.       select {
  8.          case &lt;-to.C:
  9.            return // timeout
  10.          case &lt;-ticker:
  11.            if checkSuccess() {
  12.              return
  13.            }
  14.       }
  15.    }
  16. }
  18. </details>
  22. # 答案2
  23. **得分**: 3
  25. 我更喜欢在这种情况下使用`context.Context`，这样实用函数可以更容易地适应各种真实场景。
  27. 我还会返回一些东西，比如`error`，例如从`ctx.Err()`或`bool`，以向调用者提供一些反馈（调用者可能决定无论如何都要丢弃它）：
  29. ```go
  30. func tryFunc(ctx context.Context, f func() bool) bool {
  31.     ticker := time.NewTicker(time.Second)
  32.     defer ticker.Stop()
  33.     for {
  34.         select {
  35.         case <-ctx.Done():
  36.             return false
  37.         case <-ticker.C:
  38.             if b := f(); b {
  39.                 return b
  40.             }
  41.         }
  42.     }
  43. }

Playground: https://go.dev/play/p/Iz_urEkBMIi

注意：确保上下文有超时。context.Background()没有超时。

英文:

I prefer using context.Context in cases like this, so that the utility function can more easily be adapted to a variety of real world scenarios.

I would also return something, maybe error, e.g. from ctx.Err() or the bool, to give some feedback to the caller (the caller may decide to discard it anyway):

  1. func tryFunc(ctx context.Context, f func() bool) bool {
  2. 	ticker := time.NewTicker(time.Second)
  3. 	defer ticker.Stop()
  4. 	for {
  5. 		select {
  6. 		case &lt;-ctx.Done():
  7. 			return false
  8. 		case &lt;-ticker.C:
  9. 			if b := f(); b {
  10. 				return b
  11. 			}
  12. 		}
  13. 	}
  14. }

Playground: https://go.dev/play/p/Iz_urEkBMIi

PS: make sure the context has a timeout. context.Background() doesn't

huangapple
  • 本文由 发表于 2022年1月21日 05:22:51
  • 转载请务必保留本文链接：https://go.coder-hub.com/70793565.html
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