其他函数可以共享单个defer func（）吗？

Question

I see a lot of examples using defer func() inside of a function. Is there a way to keep from repeating it in various places and call it like a normal function?

In this example (and many others) the defer function is nested inside of another function:

package main

import (
    "fmt"
    "os"
)

func main() {
    defer func() {
        if err := recover(); err != nil {
            fmt.Fprintf(os.Stderr, "Exception: %v
", err)
            os.Exit(1)
        }
    }()

    file, err := os.Open(os.Args[1])
    if err != nil {
        fmt.Println("Could not open file")
    }

    fmt.Printf("%v", file)
}

Is there a way to move the defer func() outside of main() so it can be used by other functions as well?

Answer 1

You can defer any function. Where that function is defined isn't important.

This is perfectly valid:

func foo() {
    // Do foo
}


func bar() {
    defer foo()
    // Do something before foo
}

func baz() {
    defer foo()
    // Do something else before foo
}

But in this case foo() will be called once for each invocation of bar() and baz(). It's not "shared", except in the sense that you don't have to re-write an anonymous function multiple times.

Probably the most common example of this is calling Close() in a defer statement:

func foo() error {
    f, err := os.Open(...)
    if err != nil {
        return err
    }
    defer f.Close() // "Close()" is obviously not defined here
    // do something with f
}

TL;DR;

You cannot share a defer statement across functions. But as with any other function, the function invoked by defer, can be called from multiple places.