How to write golang function

With the rise of Golang language in recent years, more and more developers have begun to come into contact with and use this language for development, and Golang functions are an important part of its development. So, how to write a high-quality Golang function? Let us find out together below.

1. Function declaration

In Go, a function is declared using the keyword func, and the syntax is as follows:

func 函数名(参数列表) (返回值列表) {
    // 函数体
}

Among them, the function name follows the naming rules of identifiers, and the parameter list Both the return value list and the return value list can be empty, and multiple return value lists are separated by commas. For example:

func sayHello() {
    fmt.Println("Hello, world!")
}

func add(x int, y int) int {
    return x + y
}

func swap(x, y string) (string, string) {
    return y, x
}

2. Function parameters

In Go, function parameters are passed by value, which means that the parameters of the function will be copied to the function stack instead of Pass the reference directly. Therefore, if the value of the parameter is modified in the function, the original parameter value will not be affected, as shown below:

func main() {
    x := 10
    modify(x)
    fmt.Println(x) // 输出: 10
}

func modify(x int) {
    x = 20
}

If you want to modify the parameter value, you can use a pointer to achieve it, as shown below:

func main() {
    x := 10
    modify(&x)
    fmt.Println(x) // 输出: 20
}

func modify(x *int) {
    *x = 20
}

Note that you need to use & to get the variable address and * to dereference the variable pointer.

3. Anonymous function

Anonymous function is a function type that does not need to be named and can be defined and called directly. In Go, you can use anonymous functions to implement closures, that is, access variables outside the function from within the function. For example:

func main() {
    x := 10
    add := func(y int) int {
        return x + y
    }
    fmt.Println(add(20)) // 输出: 30
}

In this example, we define an add anonymous function, which uses the external variable x to implement an addition operation.

4. Functions as parameters

In the Go language, functions are first-class citizens, and functions can be passed to another function as parameters. For example:

func main() {
    x := []int{1, 2, 3, 4, 5}
    fmt.Println(sum(x, func(v int) int {
        return v * 2
    })) // 输出: 30
}

func sum(x []int, f func(int) int) int {
    sum := 0
    for _, v := range x {
        sum += f(v)
    }
    return sum
}

In this example, we define a sum function that receives an array of integers and a function for processing integers. We pass the function as a parameter to the sum function and use the passed function to process each element in the array, ultimately implementing the sum operation.

5. Variable parameters

The Go language supports variable parameter functions, that is, the number of function parameters can be uncertain. We can use the ... operator to achieve this functionality. For example:

func main() {
    fmt.Println(add(1, 2, 3, 4, 5)) // 输出: 15
}

func add(nums ...int) int {
    sum := 0
    for _, num := range nums {
        sum += num
    }
    return sum
}

In this example, we define an add function that receives any number of int type parameters and returns their sum. A variadic argument is actually a slice, and we can operate on it just like a slice.

In short, the writing of Golang functions is one of the cores of Golang development and is crucial to the writing of high-quality code. Here we give a brief introduction to the basic knowledge of Golang functions, hoping to help Golang developers better understand the use of Golang functions.

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