11.2 使用Channel等待任务结束

一、等待任务

1. 手动编写等待任务

   package main
   
   import (
   	"fmt"
   )
   
   func doWorker(id int, c chan int, done chan bool) {
   	for n := range c {
   		fmt.Printf("Worker %d received %c \n", id, n)
   		// 通知外部打印完成，防止外部循环等待(大小写一起等待反馈)
   		go func() {
   			done <- true   // 如果下面每组输入输出结束后直接接收，则只有这句即可
   		}()
   	}
   }
   
   type worker struct {
   	id   chan int
   	done chan bool
   }
   
   func createWorker(i int) worker {
   	w := worker{
   		id:   make(chan int),
   		done: make(chan bool),
   	}
   	go doWorker(i, w.id, 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 {
   		worker.id <- 'a' + i
   	}
   	for i, worker := range workers {
   		worker.id <- 'A' + i
   	}
   
   	// 大小写一起等待输出
   	for _, worker := range workers {
   		<-worker.done
   		<-worker.done
   	}
   }
   
   func main() {
   	chanDemo()
   }

2. 使用go的WaitGroup进行等待

   package main
   
   import (
   	"fmt"
   	"sync"
   )
   
   func doWorker(id int, c chan int, wg *sync.WaitGroup) {
   	for n := range c {
   		fmt.Printf("Worker %d received %c \n", id, n)
   		// 通知外部打印完成
   		wg.Done()
   	}
   }
   
   type worker struct {
   	id chan int
   	wg *sync.WaitGroup
   }
   
   func createWorker(i int, wg *sync.WaitGroup) worker {
   	w := worker{
   		id: make(chan int),
   		wg: wg,
   	}
   	go doWorker(i, w.id, wg)
   	return w
   }
   
   func chanDemo() {
   
       // 使用sync.WaitGroup进行等待
   	var wg sync.WaitGroup
   
   	var workers [10]worker
   	for i := 0; i < 10; i++ {
   		workers[i] = createWorker(i, &wg)
   	}
   
   	wg.Add(20) // 有多少个任务，这里赋值20，如果少了会报错！！！
   	for i, worker := range workers {
   		worker.id <- 'a' + i
   	}
   
   	for i, worker := range workers {
   		worker.id <- 'A' + i
   	}
   
   	wg.Wait() // 等待任务昨晚
   
   }
   
   func main() {
   	chanDemo()
   }