channel

channel

package main

import (
  "fmt"
)

func main() {
  // 创建一个无缓存的channel
  messages := make(chan string)

  go func() {
    // 发送消息到 channel
    messages <- "ping"
  }()

  // 从channel中接收消息
  msg := <-messages
  fmt.Println(msg)  // ping
}

package main

import (
  "fmt"
  "time"
)

func main() {
  channelWithCache()
  channelWithoutCache()
}

func channelWithCache() {
  // 创建一个带缓冲的channel
  ch := make(chan string, 1)
  go func() {
    ch <- "Hello, first message from channel"
    time.Sleep(time.Second)
    ch <- "Hello, second message from channel"
  }()

  time.Sleep(2 * time.Second)
  message := <-ch
  fmt.Println(time.Now().String() + message)  // first message from channel
  message = <-ch
  fmt.Println(time.Now().String() + message)  // second message from channel
}

func channelWithoutCache() {
  // 不带缓冲的channel
  ch := make(chan string)
  go func() {
    time.Sleep(time.Second)
    ch <- "Hello, message from channel"
  }()

  message := <-ch
  fmt.Println(message)  // Hello, message from channel
}

select

package main

import (
  "fmt"
  "sync"
)

func task(ch1 chan int, ch2 chan string, wait *sync.WaitGroup) {
  defer wait.Done()
  for i := 0; i < 5; i++ {
    ch1 <- i
    ch2 <- fmt.Sprintf("数据：%d", i)
  }
  close(ch1)
  close(ch2)
}

func fn1(ch chan int) {
  ch <- 1
  ch <- 2
  ch <- 3
  close(ch)
}

func main() {
  ch1 := make(chan int)
  go fn1(ch1)

  for {
    select {
    case val, ok := <-ch1:
      if !ok {
        return
      }
      fmt.Println("ch1:", val, ok)
    }
  }
}