使用Channel等待任务结束

示例1：接收者主动通知发送者已经完成任务

func doWork(id int, c chan int, done chan bool) {
    for n := range c {
        fmt.Printf("Worker %d received %c\n", id, n)
        done <- true
    }
}
type worker struct {
    in chan int
    done chan bool
}
func createWorker(id int) worker {
    w := worker{
        in: make(chan int),
        done: make(chan bool),
    }
    go doWork(id, w.in, w.done)
    return w
}
func chanDemo() {
    var workers [10]worker
    for i := 0; i < 10; i++ {
        workers[i] = createWorker(i)
    }
    for i, worker := range workers {
        workers.in <- 'a' + i
    }
    for _, worker := range workers {
        <-worker.done
    }
    for i, worker := range workers {
        workers.in <- 'A' + i
    }
    for _, worker := range workers {
        <-worker.done
    }
}
func main() {
    chanDemo()
}

示例2：使用waitGroup来等待多个任务完成

func doWork(id int, c chan int, wg *sync.WaitGroup) {
    for n := range c {
        fmt.Printf("Worker %d received %c\n", id, n)
        wg.Done() // 任务完成
    }
}

type worker struct {
    in chan int
    wg *sync.WaitGroup
}

func createWorker(id int, wg *sync.WaitGroup) worker {
    w := worker{
        in: make(chan int),
        wg: wg,
    }
    go doWork(id, w.in, wg)
    return w
}

func chanDemo() {
    var wg sync.WaitGroup

    var workers [10]worker
    for i := 0; i < 10; i++ {
        workers[i] = createWorker(i, &wg)
    }

    wg.Add(20) // 添加20个任务
    for i, worker := range workers {
        workers.in <- 'a' + i
    }

    for i, worker := range workers {
        workers.in <- 'A' + i
    }

    wg.Wait() // 等待任务完成
}

func main() {
    chanDemo()
}

将上述代码进行包装(重构)：

func doWork(id int, w worker) {
    for n := range w.in {
        fmt.Printf("Worker %d received %c\n", id, n)
        w.done()
    }
}

type worker struct {
    in chan int
    done func()
}

func createWorker(id int, wg *sync.WaitGroup) worker {
    w := worker{
        in: make(chan int),
        done: func() {
            wg.Done() // 任务完成
        },
    }
    go doWork(id, w)
    return w
}

func chanDemo() {
    var wg sync.WaitGroup

    var workers [10]worker
    for i := 0; i < 10; i++ {
        workers[i] = createWorker(i, &wg)
    }

    wg.Add(20) // 添加20个任务
    for i, worker := range workers {
        workers.in <- 'a' + i
    }

    for i, worker := range workers {
        workers.in <- 'A' + i
    }

    wg.Wait() // 等待任务完成
}

func main() {
    chanDemo()
}