Detailed explanation of the difference between the receiver of a method in golang being a pointer and not being a pointer

The following tutorial column will give you a detailed explanation of the difference between the receiver of a method in golang being a pointer and not being a pointer. I hope it will be helpful to friends in need!

The difference between the receiver of a method in golang being a pointer and not being a pointer

Preface

Recently, I read a website and a student asked me what is the difference between the receiver of a method in golang being a pointer and not being a pointer. Here I will explain it in a simple and easy-to-understand way to help students who have just learned golang.

What is the method

In fact, as long as you understand this principle, you can basically understand the problems mentioned above.

The method is actually a special function, and the receiver is the first parameter passed in implicitly. .

For example

type test struct{
    name string
}

func (t test) TestValue() {
}

func (t *test) TestPointer() {
}

func main(){
    t := test{}
    
    m := test.TestValue
    m(t)
    
    m1 := (*test).TestPointer
    m1(&t)    
}

Is it easy to understand? Now let’s add code to see the difference between pointers and non-pointers.

type test struct{
    name string
}

func (t test) TestValue() {
    fmt.Printf("%p\n", &t)
}

func (t *test) TestPointer() {
    fmt.Printf("%p\n", t)
}

func main(){
    t := test{}
    //0xc42000e2c0
    fmt.Printf("%p\n", &t)
    
    //0xc42000e2e0
    m := test.TestValue
    m(t)
    
    //0xc42000e2c0
    m1 := (*test).TestPointer
    m1(&t)    

}

It is estimated that some students have understood that when the actual parameter is not a pointer, the value is copied. Therefore, every time TestValue() is called, the value is copied.

If it involves the operation of modifying the value, What will be the result?

type test struct{
    name string
}

func (t test) TestValue() {
    fmt.Printf("%s\n",t.name)
}

func (t *test) TestPointer() {
    fmt.Printf("%s\n",t.name)
}

func main(){
    t := test{"wang"}

    //这里发生了复制,不受后面修改的影响
    m := t.TestValue
    
    t.name = "Li"
    m1 := (*test).TestPointer
    //Li
    m1(&t)    
    
    //wang
    m()
}

So all students must pay attention when encountering such problems in programming.

What is the relationship between these method sets? Here I borrowed from qyuhen's study in golang As for taking notes, I also recommend friends who like golang to read this book, which will be of great help in deepening their understanding of golang.

• Type T method set contains all receiver T methods.
• The type

T method set contains all receiver T

T methods.

• If type S contains anonymous field T, then S method set contains T method.
• If type S contains anonymous field T, then S's method set contains T T methods.
• Regardless of embedding T or
T, the set of S methods always contains T *T methods.
Conclusion

Although golang is simple and easy to use, it still has many pitfalls. The author encountered many pitfalls in the process of using golang, which will be mentioned in the blog later. Everyone is welcome. discuss together.

The above is the detailed content of Detailed explanation of the difference between the receiver of a method in golang being a pointer and not being a pointer. For more information, please follow other related articles on the PHP Chinese website!