golang defer anonymous method

Golang is an open source programming language designed and maintained by Google. In Golang, the defer statement is used to execute a piece of code after the function execution ends. Typically, the defer statement is used to clean up resources, such as closing a file or unlocking a mutex.

However, there is a more powerful feature of using defer in Golang: anonymous methods. This feature allows you to execute an anonymous function before the function's return value is set.

Let’s look at a simple example to show how anonymous functions use defer in Golang.

func foo() (result int) {
    defer func() {
        fmt.Println("defer")
        result += 100
    }()
    fmt.Println("before")
    result = 1
    fmt.Println("after")
    return
}

func main() {
    fmt.Println(foo())
}

There is a defer statement in function foo(), which contains an anonymous function. The anonymous function will be executed before the return value of the foo() function is set. In this example, the defer statement is executed before the result variable is returned.

The output is as follows:

before
after
defer
101

We can see that the program first prints out the "before" and "after" strings, and then the anonymous function in the defer statement prints out the "defer" string . Finally, the foo() function returns 101, not 1. This is because the anonymous function modifies the value of the result variable before it is returned.

This example demonstrates how to use defer and anonymous functions in Golang to achieve some very interesting functions. We can use this method to record function calls, record function performance information, perform some stray cleanup work, etc.

In addition, there are many other useful scenarios that can be implemented using defer and anonymous functions. For example, operating critical sections under the protection of a mutex, or ensuring that file handles are closed correctly when processing files, etc.

Summary: In Golang, the defer statement is very powerful and can be used with anonymous functions. This feature can execute a piece of code before the function's return value is set, helping us implement some special functions. Understanding this feature can greatly improve our ability to write code in Golang.

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