A pointer is a value that represents a memory address . This memory address is often the starting location of the value of another variable stored in memory .Go Language support for pointers is between Java Language and C/C++ Between languages , It didn't want to Java Language like that cancels the ability of the code to directly operate the pointer , Also avoided C/C++ The security and reliability problems caused by the abuse of pointer in language .

Basic operation

Go Although the language retains the pointer , But unlike other programming languages ：

• The default value is nil, No, NULL Constant
• The operator “&” Take the variable address , “*” Access the target object through the pointer
• Pointer operation not supported , I won't support it “->” Operator , direct ⽤ “.” Visit the target members

new function

expression new(T) Will create a T Anonymous variable of type , What has been done is to T New value of type allocates and clears a block of memory space , Then return the address of this memory space as the result , And the result is pointing to this new T Pointer value of type value , The returned pointer type is *T.

func main() {
    
    var p1 *int
    p1 = new(int)              //p1 by *int  type ,  Point to anonymous int Variable 
    fmt.Println("*p1 = ", *p1) //*p1 = 0

    p2 := new(int) //p2 by *int  type ,  Point to anonymous int Variable 
    *p2 = 111
    fmt.Println("*p2 = ", *p2) //*p1 = 111
}

We just need to use new() function , Don't worry about the life cycle of its memory or how to delete it , because Go Language memory management system will help us to take care of everything .

Pointer as function parameter

func swap01(a, b int) {
    
    a, b = b, a
    fmt.Printf("swap01 a = %d, b = %d\n", a, b)
}

func swap02(x, y *int) {
    
    *x, *y = *y, *x
}

func main() {
    
    a := 10
    b := 20

    //swap01(a, b) // Value passed 
    swap02(&a, &b) // Variable address passing 
    fmt.Printf("a = %d, b = %d\n", a, b)
}