Go基础编程实践（七）—

同时运行多个函数

观察常规代码和并发代码的输出顺序。

// 常规代码，顺序执行，依次输出

package main

import (

    "fmt"

    "time"

)

func main() {

    strN := []string{"a", "b", "c", "d"}

    for _, strV := range strN {

        time.Sleep(time.Second)

        fmt.Println(strV)

    }

    intN := []int{1, 2, 3, 4}

    for _, intV := range intN {

        time.Sleep(time.Second)

        fmt.Println(intV)

    }

}

// 并发代码，并发执行，无序输出

package main

import (

    "fmt"

    "time"

)

func main() {

    go func() {

        strN := []string{"a", "b", "c", "d"}

        for _, strV := range strN {

            time.Sleep(time.Second)

            fmt.Println(strV)

        }

    }()

    go func() {

        intN := []int{1, 2, 3, 4}

        for _, intV := range intN {

            time.Sleep(time.Second)

            fmt.Println(intV)

        }

    }()

    // 防止main routine过早退出

    time.Sleep(10 * time.Second)

}

通道的关闭

// 生产者关闭通道

package main

import (

    "time"

    "fmt"

)

func main() {

    channel := make(chan string)

    go func() {

        names := []string{"Jack", "Mike", "John", "Kitty"}

        for _, name := range names {

            time.Sleep(time.Second)

            // fmt.Println(name)

            channel <- name

        }

        // 发送完毕关闭通道，否则引起死锁

        close(channel)

    }()

    for data := range channel {

        fmt.Println(data)

    }

}

在通道中传递数据

// 利用无缓冲通道同步传递数据

package main

import "fmt"

func main(){

  nameChannel := make(chan string)

  done := make(chan string)

  go func(){

    names := []string {"tarik", "michael", "gopi", "jessica"}

    for _, name := range names {

      fmt.Println("Processing the first stage of: " + name)

      nameChannel <- name

    }

    close(nameChannel)

  }()

  go func(){

    for name := range nameChannel{

      fmt.Println("Processing the second stage of: " + name)

    }

    done <- ""

  }()

  <-done

}

// 利用有缓冲通道传递数据，提高性能

package main

import "fmt"

func main(){

  nameChannel := make(chan string, 5)

  done := make(chan string)

  go func(){

    names := []string {"tarik", "michael", "gopi", "jessica"}

    for _, name := range names {

      fmt.Println("Processing the first stage of: " + name)

      nameChannel <- name

    }

    close(nameChannel)

  }()

  go func(){

    for name := range nameChannel{

      fmt.Println("Processing the second stage of: " + name)

    }

    done <- ""

  }()

  <-done

}

并发等待

package main

import (

    "fmt"

    "sync"

)

func main() {

    var wg sync.WaitGroup

    for i := 0; i < 10; i++ {

        // 遍历一次，增加一次计数

        wg.Add(1)

        go func(){

            fmt.Println("Hello World")

            // 执行一次，减少一次计数

            wg.Done()

        }()

    }

    // 等待计数归零，结束程序

    wg.Wait()

}

// 利用通道等待

package main

import (

    "time"

    "fmt"

)

func main() {

    channel := make(chan string)

    go func() {

        names := []string{"Jack", "Mike", "John", "Kitty"}

        for _, name := range names {

            time.Sleep(time.Second)

            fmt.Println(name)

            // channel <- name

        }

        // 遍历完毕向通道发送数据，告诉main routine已执行完毕

        channel <- ""

    }()

    // main routine收到数据，退出程序

    // 因为只是为了同步，不需要通道中的数据，所以将数据抛弃

    <-channel

}

选择并发结果

package main

import (

    "time"

    "fmt"

)

func main() {

    channel1 := make(chan string)

    channel2 := make(chan string)

    go func(){

        time.Sleep(1*time.Second)

        channel1 <- "Hello from channel1"

    }()

    go func(){

        time.Sleep(1 * time.Second)

        channel2 <- "Hello from channel2"

    }()

    var result string

    // select随机选择满足条件的case

    select {

    case result = <-channel1:

        fmt.Println(result)

    case result = <-channel2:

        fmt.Println(result)

    }

}

巴特西

Go基础编程实践（七）—— 并发

同时运行多个函数

通道的关闭

在通道中传递数据

并发等待

选择并发结果

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