Go channel 关闭和广播

王小明_HIT

发布于 2021-04-30 11:24:20

1.1K0

发布于 2021-04-30 11:24:20

文章被收录于专栏：程序员奇点

Go channel 关闭和广播

Dont Communicate by sharing memory, sharing memory by communicate.
不要通过共享内存的方式通讯，要通过通讯的方式共享内存

Channel 基本概念

一个通道相当于 FIFO 的队列，通道中各个元素之间都是严格按照发送的顺序队列，先发送的队列一定会被先接收，元素值的发送和传输和发送都使用到操作符 <-

channel 的关闭

向关闭的 channel 发送数据，会导致 panic

package main

import (
 "fmt"
 "sync"
 "testing"
)

func dataProducer(ch chan int, wg *sync.WaitGroup) {
 go func() {
  for i := 0; i < 11; i++ {
   ch <- i
  }
  wg.Done()
 }()
}

func dataConsumer(ch chan int , wg *sync.WaitGroup) {
 go func () {
  for i := 0; i < 10; i++ {
   data := <- ch
   fmt.Println(data)
  }
  close(ch)
  wg.Done()
 }()
}

func TestCloseChanner(t *testing.T) {
 var wg sync.WaitGroup
 ch := make(chan int)

 wg.Add(1)
 dataProducer(ch, &wg)
 wg.Add(1)
 dataConsumer(ch, &wg)
 wg.Wait()
}

运行结果

GOROOT=C:\Go #gosetup
GOPATH=D:\GoWorkSpace #gosetup
C:\Go\bin\go.exe test -c -o C:\Users\wangm\AppData\Local\Temp\___channel_close_test_go.exe GoProject/src/main/gobase/channel #gosetup
C:\Go\bin\go.exe tool test2json -t C:\Users\wangm\AppData\Local\Temp\___channel_close_test_go.exe -test.v -test.run ^\QTestCloseChanner\E$ #gosetup
=== RUN   TestCloseChanner
0
1
2
3
4
5
6
7
8
9
panic: send on closed channel

goroutine 20 [running]:
GoProject/src/main/gobase/channel.dataProducer.func1(0xc0000862a0, 0xc0000942b0)
 D:/GoWorkspaces/GoProject/src/main/gobase/channel/channel_close_test.go:12 +0x4a
created by GoProject/src/main/gobase/channel.dataProducer
 D:/GoWorkspaces/GoProject/src/main/gobase/channel/channel_close_test.go:10 +0x50
Process finished with exit code 1

v, ok <- ch; ok 为 bool 值， true 表示正常接收，false 表示通道关闭
所有的 channel 接收者都会在 channel 关闭时，立刻从阻塞等待中返回且上述 ok 值为 false 。这个广播机制被利用，进行多个订阅同时发送信号。

package main

import (
 "fmt"
 "sync"
 "testing"
)

func dataProducer(ch chan int, wg *sync.WaitGroup) {
 go func() {
  for i := 0; i < 10; i++ {
   ch <- i
  }
  close(ch)
  wg.Done()
 }()
}

func dataConsumer(ch chan int , wg *sync.WaitGroup) {
 go func () {
  for i := 0; i < 10; i++ {
   if data, ok := <- ch; ok {
    fmt.Println(data)
   } else {
    break
   }
  }
  wg.Done()
 }()
}

func TestCloseChanner(t *testing.T) {
 var wg sync.WaitGroup
 ch := make(chan int)

 wg.Add(1)
 dataProducer(ch, &wg)
 wg.Add(1)
 dataConsumer(ch, &wg)
 wg.Wait()
}

运行结果

GOROOT=C:\Go #gosetup
GOPATH=D:\GoWorkSpace #gosetup
C:\Go\bin\go.exe test -c -o C:\Users\wangm\AppData\Local\Temp\___channel_close_test_go.exe GoProject/src/main/gobase/channel #gosetup
C:\Go\bin\go.exe tool test2json -t C:\Users\wangm\AppData\Local\Temp\___channel_close_test_go.exe -test.v -test.run ^\QTestCloseChanner\E$ #gosetup
=== RUN   TestCloseChanner
0
1
2
3
4
5
6
7
8
9
--- PASS: TestCloseChanner (0.00s)
PASS

Process finished with exit code 0

测试代码

package main

import (
 "fmt"
 "sync"
 "testing"
)

func dataProducer(ch chan int, wg *sync.WaitGroup) {
 go func() {
  for i := 0; i < 10; i++ {
   ch <- i
  }
  close(ch)
  wg.Done()
 }()
}

func dataConsumer(ch chan int , wg *sync.WaitGroup) {
 go func () {
  for i := 0; i < 11; i++ {
   data := <- ch
   fmt.Println(data)
  }
  wg.Done()
 }()
}

func TestCloseChanner(t *testing.T) {
 var wg sync.WaitGroup
 ch := make(chan int)

 wg.Add(1)
 dataProducer(ch, &wg)
 wg.Add(1)
 dataConsumer(ch, &wg)
 wg.Wait()
}

运行结果：

GOPATH=D:\GoWorkSpace #gosetup
C:\Go\bin\go.exe test -c -o C:\Users\wangm\AppData\Local\Temp\___channel_close_test_go.exe GoProject/src/main/gobase/channel #gosetup
C:\Go\bin\go.exe tool test2json -t C:\Users\wangm\AppData\Local\Temp\___channel_close_test_go.exe -test.v -test.run ^\QTestCloseChanner\E$ #gosetup
=== RUN   TestCloseChanner
0
1
2
3
4
5
6
7
8
9
0
--- PASS: TestCloseChanner (0.00s)
PASS

Process finished with exit code 0

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原始发表：2021-04-18，如有侵权请联系 cloudcommunity@tencent.com 删除