How to use golang pointers

Go is a programming language that supports pointers. Pointers are widely used in Go programming because many operations require direct manipulation of memory addresses. Learning how to use pointers correctly can make your code more efficient and help solve problems in certain scenarios.

What is a pointer

A pointer is a special variable that stores an address. This address points to the address of another variable stored in memory. In other words, a pointer is the memory address of a variable.

For example:

var a int = 10
var p *int = &a

Here, a stores an integer value 10, while p is a ## A pointer variable of type #int stores the memory address of a. By &a taking out the address of a and storing it to p, we can access the address stored by a through p value.

Operations of pointers

In Go programming, pointers can perform basic operations. The following are some commonly used pointer operations:

Get the pointer address

&

You can get the pointer address of the variable by adding

& before the variable. For example:

var a int = 10
var p *int = &a

Dereference

*

Pointer variables can be dereferenced by prefixing them with

*. This converts the pointer variable to the original value pointed to by the pointer. For example:

var a int = 10
var p *int = &a

fmt.Println(*p) // 输出：10

Pointer arithmetic

and -

Pointer variables can perform addition and subtraction operations. This operation will move the address pointed to by the pointer. For example:

var a [3]int = [3]int{1, 2, 3}
var p *int = &a[0]

fmt.Println(*p) // 输出：1
p++
fmt.Println(*p) // 输出：2

In this example, we define an integer array

a and store the address of its first element in the pointer variable p. We first print out the value pointed to by p, then move the pointer to the second element in the array via p and print out the new pointer value again.

Application of pointers

The main reason for using pointers is to allow us to perform direct memory operations on variables. This makes pointers very useful in the following scenarios:

Avoid copying

Using pointers to pass parameters can avoid copying function parameters. This can reduce the memory usage of your program and can reduce the time it takes to call functions.

For example:

func swap(a, b *int) {
    temp := *a
    *a = *b
    *b = temp
}

func main() {
    x, y := 1, 2
    swap(&x, &y)
    fmt.Println(x, y) // 输出：2 1
}

In this example, we define a

swap function that accepts two integer pointers as parameters. Inside the function, we dereference the pointer and swap the values ​​of the two variables. When we call the function, we pass the addresses of the two variables to the swap function, so that the function can directly operate the memory addresses of the two variables.

Dynamic memory allocation

Pointers can be used for dynamic memory allocation. In Go programs, we can use the

new function to allocate memory and return the address of the newly allocated memory. For example:

p := new(int)
*p = 10
fmt.Println(*p) // 输出：10

In this example, we use the

new function to allocate a new int type of memory space and store the address in p middle. We then set the value of the newly allocated memory to 10 by *p = 10. Finally, we use *p to access the value and print it out.

Return multiple values

Go functions can return multiple values, one of the common uses is to return the execution status of the function and error information. In this case we usually return a pointer to the error. For example:

func add(a, b int) (int, *error) {
    if a < 0 || b < 0 {
        err := errors.New("arguments must be non-negative")
        return 0, &err
    }
    return a + b, nil
}

func main() {
    result, err := add(1, -2)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(result)
}

In this example, we define the

add function to calculate the sum of the input parameters. If either argument is negative, we create an error object and return it as a pointer. In the main function, we check whether the error pointer is nil, and if not, print the error message, otherwise print the return value of the function.

Summary

Pointers are a very useful programming tool that allow us to directly manipulate memory addresses to improve program performance and solve problems in some scenarios. By learning the basic operations of pointers and applying them to appropriate scenarios, we can write efficient and reliable Go code.

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