Go 学习笔记09.管道常见操作

心已赠人 2023-05-21 11:58 94阅读 0赞

## 管道超时处理 ##

package main
    
    import "time"
    import "fmt"
    
    func main() { 
    
        c1 := make(chan string, 1)
        go func() { 
            time.Sleep(time.Second * 2)
            c1 <- "result 1"
        }()
    
        // timeout 1
        select { 
        case res := <-c1:
            fmt.Println(res)
        case <-time.After(time.Second * 1):
            fmt.Println("timeout 1")
        }
    
        // result 2
        c2 := make(chan string, 1)
        go func() { 
            time.Sleep(time.Second * 2)
            c2 <- "result 2"
        }()
        select { 
        case res := <-c2:
            fmt.Println(res)
        case <-time.After(time.Second * 3):
            fmt.Println("timeout 2")
        }
    }

timeout 1
    result 2

## 非阻塞管道操作 ##

package main
    
    import "fmt"
    
    func main() { 
        messages := make(chan string)
        signals := make(chan bool)
    
        // 非阻塞管道，就是当<-messages中有值，触发case,没有存储值则直接default，没有时间上的等待
        select { 
        case msg := <-messages:
            fmt.Println("received message", msg)
        default:
            fmt.Println("no message received")
        }
    
        // 一个非阻塞发送的实现方法和上面一样。
        msg := "hi"
        select { 
        case messages <- msg:
            fmt.Println("sent message", msg)
        default:
            fmt.Println("no message sent")
        }
    
        // default前 也可以有多个case，都没有值存储则执行default
        select { 
        case msg := <-messages:
            fmt.Println("received message", msg)
        case sig := <-signals:
            fmt.Println("received signal", sig)
        default:
            fmt.Println("no activity")
        }
    }

no message received
    no message sent
    no activity

## 管道的关闭 ##

package main
    
    import "fmt"
    
    
    func main() { 
        jobs := make(chan int, 5)
        done := make(chan bool)
    
        go func() { 
            for { 
                // 如果管道被关闭，并且已经取出所有的值，则more是false
                j, more := <-jobs
                if more { 
                    fmt.Println("received job", j)
                } else { 
                    fmt.Println("received all jobs")
                    done <- true
                    return
                }
            }
        }()
    
        for j := 1; j <= 3; j++ { 
            jobs <- j
            fmt.Println("sent job", j)
        }
        close(jobs)
        fmt.Println("sent all jobs")
        // done 管道只是用来阻塞用的吗，上一章实践过的一种同步方法
        <-done
    }

## 管道的遍历 ##

> for range 遍历

package main
    
    import "fmt"
    
    func main() { 
    
        queue := make(chan string, 2)
        queue <- "one"
        queue <- "two"
        close(queue)
    
        // for range 遍历
        for elem := range queue { 
            fmt.Println(elem)
        }
    }