如何在不使用 time.Sleep 的情况下等待所有 goroutines 完成? [英] How to wait for all goroutines to finish without using time.Sleep?

问题描述

此代码选择同一文件夹中的所有 xml 文件，作为调用的可执行文件，并在回调方法中对每个结果异步应用处理(在下面的示例中，仅打印出文件名).

This code selects all xml files in the same folder, as the invoked executable and asynchronously applies processing to each result in the callback method (in the example below, just the name of the file is printed out).

如何避免使用 sleep 方法来防止 main 方法退出?我在处理频道时遇到问题(我认为这就是同步结果所需要的)，因此非常感谢您的帮助！

How do I avoid using the sleep method to keep the main method from exiting? I have problems wrapping my head around channels (I assume that's what it takes, to synchronize the results) so any help is appreciated!

package main

import (
    "fmt"
    "io/ioutil"
    "path"
    "path/filepath"
    "os"
    "runtime"
    "time"
)

func eachFile(extension string, callback func(file string)) {
    exeDir := filepath.Dir(os.Args[0])
    files, _ := ioutil.ReadDir(exeDir)
    for _, f := range files {
            fileName := f.Name()
            if extension == path.Ext(fileName) {
                go callback(fileName)
            }
    }
}


func main() {
    maxProcs := runtime.NumCPU()
    runtime.GOMAXPROCS(maxProcs)

    eachFile(".xml", func(fileName string) {
                // Custom logic goes in here
                fmt.Println(fileName)
            })

    // This is what i want to get rid of
    time.Sleep(100 * time.Millisecond)
}

推荐答案

您可以使用 sync.WaitGroup.引用链接的例子:

You can use sync.WaitGroup. Quoting the linked example:

package main

import (
        "net/http"
        "sync"
)

func main() {
        var wg sync.WaitGroup
        var urls = []string{
                "http://www.golang.org/",
                "http://www.google.com/",
                "http://www.somestupidname.com/",
        }
        for _, url := range urls {
                // Increment the WaitGroup counter.
                wg.Add(1)
                // Launch a goroutine to fetch the URL.
                go func(url string) {
                        // Decrement the counter when the goroutine completes.
                        defer wg.Done()
                        // Fetch the URL.
                        http.Get(url)
                }(url)
        }
        // Wait for all HTTP fetches to complete.
        wg.Wait()
}

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