channel

channel定义

make(chan Type) //等价于make(chan Type, 0)，无缓冲channel
make(chan Type, capacity) //capacity,缓冲值

channel使用

channel <- value //传递值给channel
<-channel //接收channel值，并丢弃
x := <-channel //接收搜channel值
x,ok := <-channel //接收channel值，同时检查channel是否结束或为空

无缓冲channel

有缓冲channel

关闭channel

package main
import (
    "fmt"
)
func main() {
    channel := make(chan int, 2)
    //创建一个goroutine
    go func() {
        defer fmt.Println("goroutine 结束")
        for i := 0; i < 4; i++ {
            channel <- i
            fmt.Println("goroutine 开始存值", i)
        }
        close(channel)
    }()
    for {
        //同上功能，但会检查返回的channel值是否为空或传递是否结束
        if v, ok := <-channel; ok {
            fmt.Println("接收完成", v)
        }else{
            break
        }
    }
    fmt.Println("main结束")
}

channel与range

package main
import (
    "fmt"
)
func main() {
    channel := make(chan int, 2)
    //创建一个goroutine
    go func() {
        defer fmt.Println("goroutine 结束")
        for i := 0; i < 4; i++ {
            channel <- i
            fmt.Println("goroutine 开始存值", i)
        }
        close(channel)
    }()
    for v := range channel {
        fmt.Println("接收完成", v)
    }
    fmt.Println("main结束")
}

channel与select

单流程在channel只能监听一个channel状态，select可以监听多个channel状态，如果多个case同时满足会随机选择一个执行，当select无case时会阻塞

package main
import "fmt"
func test(channel1, channel2 chan int) {
    x, y := 1, 1
    for {
        select {
        case channel1 <- x:
            x = y
            y = x + y
        case <-channel2:
            fmt.Println("quit")
            return
        }
    }
}
func main() {
    channel1 := make(chan int)
    channel2 := make(chan int)
    go func() {
        for i := 0; i < 10; i++ {
            fmt.Println(<-channel1)
        }
        channel2 <- 0
    }()
    test(channel1,channel2)
}

实现work_pool

package main
import (
    "fmt"
    "time"
)
func work(i int, jobs <-chan int, results chan<- int) {
    for job := range jobs {
        fmt.Println("work", i, "start")
        results <- job * 2
        fmt.Println("work", i, "end")
        time.Sleep(1*time.Second)
    }
}
func main() {
    jobs := make(chan int, 10)
    results := make(chan int, 10)
    for i := 0; i < 3; i++ {
        go work(i, jobs, results)
    }
    for i := 0; i < 5; i++ {
        jobs <- i
    }
    for i := 0; i < 5; i++ {
        <-results
    }
}