转换后的通道

huangapple
go评论127阅读模式
英文:

Go: transformed channel

问题

假设我在Go语言中有一个int类型的通道：

  1. theint := make(chan int)

我想要在一个名为"incremented"的新通道中包装这个通道：

  1. incremented := make(chan int)

使得以下代码能够正常工作：

  1. go func() { theint <- 1 }()
  2. <- incremented // 2

可以假设只有一个地方从int通道中读取数据。

如果在后台运行一个goroutine，它将能够正常工作：

  1. go func() {
  2.    for num := range theint {
  3.       incremented <- num + 1
  4.    }
  5. }

然而，我更倾向于不使用goroutine来实现，因为我无法在我的上下文中控制它。

有没有更简单的方法来实现这个功能？

我想到的一个方法类似于Python中的yield：

  1. for num in theint:
  2.      yield num + 1

在Go语言中是否有类似的实现方式？

英文:

Let's say I have an int channel in Go:

  1. theint := make(chan int)

I want to wrap this channel in a new channel called incremented

  1. incremented := make(chan int)

Such that:

  1. go func() { theint &lt;- 1 }
  2.     &lt;- incremented // 2

appended can be assumed to be the only one that reads from the int.

It will work if a run a goroutine in the background

  1. go func() {
  2.    for num := range theint {
  3.       incremented &lt;- num + 1
  4.    }
  5. }

However, I prefer to do it without a goroutine since I can't control it in my context.

Is there a simpler way to do it?

One thing that came to mind is python's yield:

  1. for num in theint:
  2.      yield num + 1

Is something like this possible in go?

答案1

得分: 2

生成器模式

你正在尝试实现的是生成器模式。在实现这种模式时，使用通道和 goroutine 是非常常见的做法。

然而，我更喜欢不使用 goroutine，因为我无法在我的上下文中控制它。

我相信问题是死锁。

致命错误：所有的 goroutine 都处于休眠状态 - 死锁！

为了避免死锁和未关闭的通道，可以使用 sync.WaitGroup。这是一种控制 goroutine 的惯用方式。

Playground

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"sync"
  6. )
  8. func incGenerator(n []int) chan int {
  9. 	ch := make(chan int)
  10. 	var wg sync.WaitGroup
  11. 	wg.Add(len(n))
  13. 	for _, i := range n {
  14. 		incremented := i + 1
  15. 		go func() {
  16. 			wg.Done()
  17. 			ch <- incremented
  18. 		}()
  19. 	}
  21. 	go func() {
  22. 		wg.Wait()
  23. 		close(ch)
  24. 	}()
  26. 	return ch
  27. }
  29. func main() {
  30. 	n := []int{1, 2, 3, 4, 5}
  31. 	for x := range incGenerator(n) {
  32. 		fmt.Println(x)
  33. 	}
  34. }
英文:

Generator pattern

What you are trying to implement is generator pattern. To use channels and goroutines for implementation of this pattern is totally common practice.

> However, I prefer to do it without a goroutine since I can't control it in my context.

I believe the problem is deadlock

> fatal error: all goroutines are asleep - deadlock!

To avoid deadlocks and orphaned (not closed) channels use sync.WaitGroup. This is an idiomatic way to control goroutines.

Playground

  1. package main
  3. import (
  4.     &quot;fmt&quot;
  5. 	&quot;sync&quot;
  6. )
  8. func incGenerator(n []int) chan int {
  9.     ch := make(chan int)
  10. 	var wg sync.WaitGroup
  11.     wg.Add(len(n))
  13. 	for _, i := range n {
  14.     	incremented := i + 1
  15. 	    go func() {
  16. 		    wg.Done()
  17. 			ch &lt;- incremented
  18.     	}()
  19. 	}
  21.     go func() {
  22. 		wg.Wait()
  23. 	    close(ch)
  24.     }()
  26. 	return ch
  27. }
  29. func main() {
  30.     n := []int{1, 2, 3, 4, 5}
  31. 	for x := range incGenerator(n) {
  32.     	fmt.Println(x)
  33. 	}
  34. }

答案2

得分: 0

你还可以考虑在一个无限循环中使用一个整数通道和一个退出通道。你也可以选择一个变量增量值。请参考下面的代码：

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"sync"
  6. 	"time"
  7. )
  9. func main() {
  11. 	var accum int //累加增量值
  12. 	var wg sync.WaitGroup
  15. 	c1 := make(chan int)
  16. 	exChan := make(chan bool)
  18. 	wg.Add(1)
  19. 	go func() {
  20. 		time.Sleep(time.Second * 1)
  21. 		c1 <- 1
  22. 		wg.Done()
  23. 	}()
  24. 	wg.Add(1)
  25. 	go func() {
  26. 		time.Sleep(time.Second * 2)
  27. 		c1 <- 2
  28. 		wg.Done()
  29. 	}()
  30. 	wg.Add(1)
  31. 	go func() {
  32. 		time.Sleep(time.Second * 2)
  33. 		c1 <- 5
  34. 		wg.Done()
  35. 	}()
  36. 	go func() {
  37. 		wg.Wait()
  38. 		close(exChan)
  39. 	}()
  41. 	for {
  42. 		var done bool
  44. 		select {
  45. 		case incBy := <-c1: //增加通道中的值
  46. 			accum += incBy
  47. 			fmt.Println("接收到的增量值为:", incBy, "; 累加值为", accum)
  48. 		case d := <-exChan:
  49. 			done = !(d)
  50. 		}
  51. 		if done == true {
  52. 			break
  54. 		}
  55. 	}
  57. 	fmt.Println("最终累加值为", accum)
  58. }

Playground: https://play.golang.org/p/HmdRmMCN7U

如果我们总是有非零的增量值，那么退出通道是不需要的。我也喜欢@I159的方法！

无论如何，希望这对你有所帮助。

英文:

One thing you can also consider is having a select on the int channel and an exit channel - in an infinite for loop. You can choose a variable increment value too. Please see code below:

  1. package main
  3. import (
  4. 	&quot;fmt&quot;
  5. 	&quot;sync&quot;
  6. 	&quot;time&quot;
  7. )
  9. func main() {
  11. 	var accum int //accumulator of incremented values
  12. 	var wg sync.WaitGroup
  15. 	c1 := make(chan int)
  16. 	exChan := make(chan bool)
  18. 	wg.Add(1)
  19. 	go func() {
  20. 		time.Sleep(time.Second * 1)
  21. 		c1 &lt;- 1
  22. 		wg.Done()
  23. 	}()
  24. 	wg.Add(1)
  25. 	go func() {
  26. 		time.Sleep(time.Second * 2)
  27. 		c1 &lt;- 2
  28. 		wg.Done()
  29. 	}()
  30. 	wg.Add(1)
  31. 	go func() {
  32. 		time.Sleep(time.Second * 2)
  33. 		c1 &lt;- 5
  34. 		wg.Done()
  35. 	}()
  36. 	go func() {
  37. 		wg.Wait()
  38. 		close(exChan)
  39. 	}()
  41. 	for {
  42. 		var done bool
  44. 		select {
  45. 		case incBy := &lt;-c1: //Increment by value in channel
  46. 			accum += incBy
  47. 			fmt.Println(&quot;Received value to increment:&quot;, incBy, &quot;; Accumulated value is&quot;, accum)
  48. 		case d := &lt;-exChan:
  49. 			done = !(d)
  50. 		}
  51. 		if done == true {
  52. 			break
  54. 		}
  55. 	}
  57. 	fmt.Println(&quot;Final accumulated value is&quot;, accum)
  58. }

Playground: https://play.golang.org/p/HmdRmMCN7U

Exit channel not needed, if we are having non-zero increments always. I like @I159 's approach too!

Anyways, hope this helps.

huangapple
  • 本文由 发表于 2017年3月9日 20:38:06
  • 转载请务必保留本文链接：https://go.coder-hub.com/42695608.html
  • channel
  • generator
  • go
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定