golang pointers are different

Golang is a high-level programming language similar to C language. Due to its simplicity, efficiency, concurrency and other characteristics, it is gradually loved and applied by more and more developers. In Golang, pointers are also an important concept, but unlike other programming languages, pointers in Golang also have their own unique characteristics and usage. This article will introduce the differences and usage of pointers in Golang.

1. What is a pointer

In Golang, a pointer is a variable whose value is the address of another variable, and the address is usually a one-byte unsigned integer. The variable pointed to is the data stored in memory, and the pointer variable only stores the address of the data. In Golang, you can use *T of reference type to represent pointer type, where T represents the data type pointed by the pointer.

For example:

var p *int

The above code defines a variable p, which is a pointer to int type. This code does not specify a specific address value for the variable p. Therefore, the current value of p is empty and it does not point to any actual variable.

2. The difference between pointers and variables

Variables in Golang can save specific values, while pointer variables save the memory address where the variable is located. The difference between variables and pointers is that variables specifically store the value of a certain data, while pointer variables store the address of the data. Therefore, when using a pointer to access a variable, the value of the variable is actually obtained through the address recorded by the pointer variable.

For example:

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

The above code first defines an integer variable a and initializes it to 10, and then defines a pointer variable p pointing to the int type in the second line and sets it Initialized to the address &a of variable a. In this way, the pointer variable p points to the address of the variable a, and we can access the value of the variable a through the pointer variable p.

3. Use of pointers

In Golang, you can use the & operator to get the address of a variable, so that we can define a pointer variable pointing to the variable in the code. If you want to use a pointer to access the value of a variable, you can use the * operator, which is called the dereferencing operator.

For example:

var a int = 10
var p *int = &a
fmt.Println(*p)

The above code outputs the value of variable a. This is because the * operator is used in the third line to dereference the pointer variable p. When writing code, we need to note that pointer types can point not only to variables, but also to data types such as functions, structures, or arrays.

4. Pointer type and nil keyword

In Golang, the nil keyword is used to represent the zero value of a pointer type variable, which represents an invalid address value. When the value of a pointer variable is nil, it means that it does not point to any actual data. Therefore, before using a pointer variable, you need to check whether its value is nil. If it is nil, you need to reallocate the memory or perform error handling according to the actual situation.

For example:

var p *int
if p == nil {
    fmt.Println("p is nil")
}

In the above code, an integer pointer variable p is first defined and its value is initialized to nil. Then, in the second line, the if statement is used to determine whether the value of the pointer variable p is nil. If it is nil, "p is nil" is output.

5. Pointer variables and function parameters

In Golang, function parameters can be pointer types. This type of parameter transfer can effectively reduce the number of function parameter transfers and memory usage. Improve code execution efficiency. When the function parameter is a pointer type, modifications to the pointer variable in the function can affect the actual external variable.

For example:

func main() {
    a := 10
    fmt.Println("Before: a =", a)
    modify(&a)
    fmt.Println("After: a =", a)
}

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

The above code first defines a variable a in the function main and initializes its value to 10. Then, call the function modify to modify the value of variable a. In the function modify, the parameter p is a pointer type, which means that the address of variable a is passed in. Through the dereference operator *p, the function modify modifies the value of variable a to 20. In function main, the value of variable a is output again and it is found that its value has been modified to 20. This shows that modifying the value of the pointer variable p in the function modify will also affect the actual variable a.

Summary

This article introduces the concepts, differences, usage and application of pointers in Golang, etc. Pointers are an important programming concept and are an integral part of Golang. In actual development, you need to pay attention to the use of pointer variables, and you must pay attention to the validity of the variables they point to to avoid dangling pointers and other situations. At the same time, pointer types also need to be optimized according to actual conditions to ensure the performance and stability of the code.

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