Go语言教程：深入解析通道和选择语句 3

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package main
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import (
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  "fmt"
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  "math/rand"
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  "time"
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)
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func main() {
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  example1()
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  example2()
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}
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// 示例1。
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func example1() {
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  // 准备好几个通道。
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  intChannels := [3]chan int{
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    make(chan int, 1),
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    make(chan int, 1),
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    make(chan int, 1),
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  }
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  // 随机选择一个通道，并向它发送元素值。
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  index := rand.Intn(3)
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  fmt.Printf("The index: %d\\n", index)
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  intChannels[index] <- index
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  // 哪一个通道中有可取的元素值，哪个对应的分支就会被执行。
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  select {
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  case <-intChannels[0]:
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    fmt.Println("The first candidate case is selected.")
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  case <-intChannels[1]:
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    fmt.Println("The second candidate case is selected.")
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  case elem := <-intChannels[2]:
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    fmt.Printf("The third candidate case is selected, the element is %d.\\n", elem)
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  default:
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    fmt.Println("No candidate case is selected!")
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  }
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}
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// 示例2。
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func example2() {
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  intChan := make(chan int, 1)
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  // 一秒后关闭通道。
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  time.AfterFunc(time.Second, func() {
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    close(intChan)
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  })
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  select {
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  case _, ok := <-intChan:
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    if !ok {
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      fmt.Println("The candidate case is closed.")
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      break
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    }
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    fmt.Println("The candidate case is selected.")
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  }
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}