Golang is a programming language that is favored by more and more developers for its simplicity, efficiency, concurrency safety and other features. Golang's functions are value types, which are highly flexible and extensible, and can easily implement closure functions.

Closure is one of the commonly used techniques in functions. It allows a function to access a variable defined in the outer scope and return a reference to this variable. Next, this article will share different examples to explain the closure application of Golang functions.

1. Calculator

The calculator is a common closure application. It uses closures to realize the self-increment or self-decrement of the counter, allowing programmers to easily manage the status of the counter.

The following is an example:

func Calculator(number int) func() int {
    return func() int {
        number += 1
        return number
    }
}

// 使用
cal := Calculator(0)
fmt.Println(cal()) // 1
fmt.Println(cal()) // 2
fmt.Println(cal()) // 3

In this example, the Calculator function returns a closure, which internally accesses the variable number defined in the Calculator function and implements auto-increment Function.

2. Loop iteration

In Golang, since there is no while loop, a for loop is generally used to implement iteration. However, in some cases it is more convenient to iterate through a loop using a closure.

The following is an example:

func Iteration() {
    items := []string{"apple", "banana", "cherry"}

    for _, item := range items {
        func() {
            fmt.Printf("%s
", item)
        }()
    }
}

// 使用
Iteration()

In this example, the Iteration function is a loop iteration function that uses a closure to print out each element in the array.

3. Delayed call

Delayed call is a commonly used function in Golang, which allows the program to perform some finishing work before the function exits. In closures, you can use delayed calls to achieve some elegant operations.

The following is an example:

func DeferCall() {
    fmt.Println("start")

    func() {
        defer func() {
            fmt.Println("end")
        }()
    }()
}

// 使用
DeferCall()

In this example, a DeferCall function is defined, a closure is defined in the function, and an anonymous function is called using defer inside the closure. The defer statement here will be executed when the function exits to implement some specific functions, such as resource release, logging, etc.

4. Concurrency control

In Golang, it is very convenient to use goroutine to achieve concurrency. However, in some cases, some special concurrency control needs to be implemented, which can be solved using closures.

The following is an example:

func ConcurrencyControl() {
    var wg sync.WaitGroup
    ch := make(chan bool, 2)

    for i := 1; i <= 2; i++ {
        wg.Add(1)

        go func(id int) {
            defer func() {
                wg.Done()
            }()

            ch <- true

            defer func() {
                <-ch
            }()

            time.Sleep(time.Second * time.Duration(2))
            fmt.Printf("id=%d
", id)
        }(i)
    }
    wg.Wait()
}

// 使用
ConcurrencyControl()

In this example, a ConcurrencyControl function is defined, which uses WaitGroup and chan to control the execution order of two concurrent threads. Among them, defer calls in closures are used to implement some specific operations.

Summary

The above examples show four application aspects of Golang function closures, but they are not all. In actual development, programmers can choose different closure application methods to meet different needs.

In general, Golang's function closure is a very useful and powerful feature. It can not only improve the efficiency and scalability of the program, but also make programmers write code more happily. It is recommended that programmers master this skill and apply it to actual development.

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