What is golang pointer usage?

Golang pointer usage includes: 1. To obtain the address of a variable, you can obtain the memory address of the variable by adding the & symbol before the variable name; 2. To access the value pointed by the pointer, by adding the * symbol before the pointer variable. You can access the value pointed to by the pointer; 3. Create a pointer variable and use the new keyword to create a zero-value pointer variable of the specified type; 4. Pass the pointer to the function, and you can pass the pointer to the function as a parameter; 5. Return the pointer so that it can be Access variables created within the function from outside the function; 6. Null pointer check to avoid null pointer reference errors, etc.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

In the Go language, a pointer is a special variable type used to store the memory address of a variable. Through pointers, the value of a variable can be directly accessed and modified. The following are the main uses of pointers in the Go language:

Get the address of a variable: You can get the memory address of a variable by adding the & symbol before the variable name. For example:

x := 10
p := &x // 获取变量x的地址

Access the value pointed to by the pointer: You can access the value pointed by the pointer by adding the * symbol in front of the pointer variable. For example:

fmt.Println(*p) // 输出指针p指向的值，即变量x的值

Creating a pointer variable: You can use the new keyword to create a zero-value pointer variable of a specified type. For example:

p := new(int) // 创建一个int类型的零值指针变量
*p = 20 // 通过指针p修改其指向的值

Passing a pointer to a function: You can pass a pointer to a function as a parameter to modify the value of the original variable inside the function. This can avoid functions copying variables and improve program performance. For example:

func updateValue(p *int) {
    *p = 30 // 修改指针p所指向的值
}
x := 10
updateValue(&x) // 将变量x的地址传递给函数

Return pointer: A function can return a value of pointer type so that variables created inside the function can be accessed outside the function. But be careful not to return the address of local variables when returning a pointer, because local variables will be destroyed after the function is executed. For example:

func createPointer() *int {
    x := 40
    return &x // 错误示例：返回局部变量x的地址
}
p := createPointer() // 错误示例：访问已被销毁的局部变量x

Null pointer check: Before using a pointer, a null pointer check should be performed to avoid null pointer reference errors. A nil value can be used to represent a null pointer. For example:

var p *int // 声明一个int类型的指针变量，默认值为nil
if p != nil {
    fmt.Println(*p) // 对非空指针进行操作
}

Pointers are often used in the following situations in the Go language:

1. When passing large data structures or objects, avoid value copying and improve program performance.

2. Modify the value of the original variable inside the function.

3. Dynamically allocate memory, create and operate complex data structures.

But be aware that excessive use of pointers may make the code difficult to understand and maintain, and may also cause problems such as memory leaks and dangling pointers. Therefore, be careful when using pointers and follow the Go language's pointer usage specifications.

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