golang method front pointer

In the Go language, we can add behaviors to objects through methods. When defining a method, we can specify the receiver. The receiver can be a value type (such as int, float) or pointer type (such as int, float), which determines whether to use value passing or Pointer passing. Using a pointer before the method name is called a pointer before method. This article will explore the pros, cons, and usage scenarios of using pointers before methods.

What is a pre-method pointer

In the Go language, declaring a method can be like this:

func (s Struct) method() {}

func (s *Struct) pointerMethod() {}

The receiver of the first method is a value type, and the receiver of the first method is a value type, and the receiver of the first method is a value type. The receiver of both methods is a pointer type.

Using a pointer before the method name of the second method is called a pre-method pointer.

Advantages of pointers before methods

1. The receiver value can be modified

The pointer before the method can modify the value pointed by the receiver, but the value type cannot.

type Person struct {
    Name string
    Age int
}

func (p *Person) SetAge(age int)  {
    p.Age = age
}

func main() {
    p := &Person{Name: "Bob", Age: 20}
    fmt.Printf("Before: %v
", p.Age)

    p.SetAge(25)
    fmt.Printf("After: %v
", p.Age)
}

Output:

Before: 20
After: 25

2. Large object copying can be avoided

When using a value type as the receiver, the method will copy the entire object. When using a pointer type as the receiver, the method only copies the pointer. Therefore, when using pointer types as receivers, you can avoid performance problems caused by large objects being copied.

type BigStruct struct {
    Data [1000000]int
}

func (s *BigStruct) method() {}

func main() {
    b := BigStruct{}
    b.method()
}

When using a value type as the receiver, calling the method method will copy the entire BigStruct object, causing performance problems. Using pointer types as receivers can avoid this problem.

Disadvantages of pointers before methods

1. May cause null pointer exception

When using a pointer type as the receiver, you need to check whether the receiver is a null pointer. Otherwise, a NullPointerException will occur when operating on the receiver within the method.

type Person struct {
    Name string
    Age int
}

func (p *Person) SetAge(age int)  {
    if p == nil {
        return
    }
    p.Age = age
}

func main() {
    var p *Person
    p.SetAge(25)
}

In the above code, p.SetAge(25) will trigger a null pointer exception because p is a null pointer. Therefore, you need to pay attention to checking the null pointer situation when using pointers before methods.

2. May affect code readability

Using pointer types as receivers may make the code difficult to understand and prone to ambiguity.

func (s *Struct) method() {}

func (s *Struct) pointerMethod() {}

func main() {
    s := Struct{}
    s.pointerMethod()
}

In the above code, s.pointerMethod() may cause readers to question: Why is the pointer method called when using a value type?

Conclusion

In Go language, using pointers before methods has its advantages and disadvantages.

When using a pointer type as the receiver, you can modify the value pointed by the receiver, avoid large object copying, etc. However, it may also cause problems such as null pointer exceptions and affect code readability.

Therefore, when using method front pointers, you need to weigh the advantages and disadvantages and choose the method that suits you. If you need to modify the value pointed to by the receiver, or avoid large object copying, you can use a pointer type as the receiver; otherwise, you can use a value type as the receiver.

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