如何在不等待另一个 goroutine 中设置的情况下读取频道？

Question

我在 goroutine 中使用通道时遇到问题。var test = make(chan string)func main() {    go initChan()    for i := 0; i < 2; i++ {        go readChan()    }    var input string    fmt.Scanln(&input)}func initChan() {    for i := 0; i < 100; i++ {        test <- "Iteration num: " + strconv.Itoa(i)        time.Sleep(time.Second * 5)    }}func readChan() {    for {        message := <- test        log.Println(message)    }}输出：2019/12/24 08:21:17 Iteration num: 02019/12/24 08:21:22 Iteration num: 12019/12/24 08:21:27 Iteration num: 22019/12/24 08:21:32 Iteration num: 32019/12/24 08:21:37 Iteration num: 42019/12/24 08:21:42 Iteration num: 5................................我需要线程读取而不等待测试变量的更新。现在每个 readChan() 都在等待 initChan() 更新测试变量。是否可以使 readChan() 线程一次工作而无需等待每个线程的 initChan() ？

Answer 1

创建了一个恶魔，它将所有消息从测试通道推送到所有其他监听程序。

var test = make(chan string)

var mapChan = make(map[int]chan string)

var count = 3

func main() {

    go initChan()

    go deamon()

    for i := 0; i < count; i++ {

        mapChan[i] = make(chan string)

        go readChan(i)

    }

    var input string

    fmt.Scanln(&input)

}

func deamon() {

    for {

        message := <-test

        for i := 0; i < count; i++ {

            mapChan[i] <- message

        }

    }

}

func initChan() {

    for i := 0; i < 100; i++ {

        test <- "Iteration num: " + strconv.Itoa(i)

        time.Sleep(time.Second * 1)

    }

}

func readChan(i int) {

    for {

        select {

        case message := <-mapChan[i]:

            log.Println(message)

        default:

            // Do for not when written on channel

        }

    }

}

Answer 2

如果我正确理解您的问题，此解决方案可能会有所帮助。我使用了一个大小为 1 的缓冲通道，因此作为发送方的 goroutine 永远不会被阻塞，这是在无缓冲通道的情况下。您可以阅读有关频道的更多信息：频道的行为

package main

import (

    "log"

    "strconv"

    "sync"

    "time"

)

// Buffered channel with size 1 guarantees delayed delivery of data

// As soon as the goroutine sends to the channel, the reciever goroutine dequeus it

// Then the reciver goroutines does the work, but the sender goroutine isn't blocked

// As the size is again 0 after the reciever recieved it but might haven't processed it yet

var test = make(chan string, 1)

func main() {

    var wg sync.WaitGroup

    wg.Add(2)

    // Waits for other goroutines to complete before the main goroutine returns

    defer wg.Wait()

    go initChan(&wg)

    go readChan(&wg)

}

func initChan(wg *sync.WaitGroup) {

    defer wg.Done()

    for i := 0; i < 100; i++ {

        // Sends continuously

        test <- "Iteration num: " + strconv.Itoa(i)

        time.Sleep(time.Second * 5)

    }

    close(test)

}

func readChan(wg *sync.WaitGroup) {

    defer wg.Done()

    var message string

    var ok bool

    // Reciever deques the value as soon as it recieves it

    // But might take time to proceed

    for {

        select {

        case message, ok = <-test:

            // If channel is closed

            if ok == false {

                return

            }

            log.Println(message)

        default:

            log.Println(message)

        }

    }

}