对指针使用延迟 [英] Using defer with pointers

问题描述

让我们说我有以下代码:

Let us say that I have the following code:

func getConnection(fileName string) *os.File {
    file, err := os.Open(fileName)
    //Check for error
    return file
}

我使用此函数打开文件，然后从执行其他活动的另一个函数调用该函数.

I use this function to open a file and the function is called from another function that does some other activity.

我的问题是，既然我已经打开文件，如何关闭它.如果我要在 getConnection()内添加 defer file.Close()，它会在返回之前关闭文件吗?在调用函数中使用defer有意义吗?

My question is, now that I have opened the file, how do I close it. If I were to add defer file.Close() inside getConnection(), wouldn't it close the file before returning? Does it make sense to use defer inside the calling function?

推荐答案

如果函数的目的是返回文件，为什么要在返回文件的函数中将其关闭?

If the purpose of your function is to return a file, why would you want to close it in the function that returns it?

在这种情况下，调用方有责任正确关闭文件，最好使用 defer :

In this case it is the responsibility of the caller to properly close the file, preferably with defer:

func usingGetConnection() {
    f := getConnection("file.txt")
    defer f.Close()
    // Use f here
}

尽管您的 getConnection()函数吞噬了错误，但是您应该使用多次返回值来表示类似这样的问题:

Although your getConnection() function swallows errors, you should use multi-return value to indicate problems like this:

func getConnection(fileName string) (*os.File, error) {
    file, err := os.Open(fileName)
    //Check for error
    if err != nil {
        return nil, err
    }
    return file, nil
}

并使用它:

func usingGetConnection() {
    f, err := getConnection("file.txt")
    if err != nil {
        panic(err) // Handle err somehow
    }
    defer f.Close()
    // Use f here
}

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