Go中的结构初始化和方法声明

Question

I am new of Go, and pretty curious of structs. Let's define a struct T

type T struct {
    size int
}

1. I have seen different types of struct initialization. What are the differences?

   new(T)     // 1
   T{size:1}  // 2
   &T{size:1} // 3
   

2. And the two types of method declarations:

   func (r *T) area() int // 1
   func (r T) area() int  // 2
   

   What should be the right way?

Answer 1

1. allocation

new and &T{size:1} returns *T

T{size:1} return T

The built-in function new takes a type T, allocates storage for a variable of that type at run time, and returns a value of type *T pointing to it. The variable is initialized as described in the section on initial values.

2.

The method set of any other named type T consists of all methods with receiver type T. The method set of the corresponding pointer type *T is the set of all methods with receiver *T or T (that is, it also contains the method set of T).

var pt *T

var t T

func (r *T) area() int

you can use pt.area() or t.area()

func (r T) area() int

you can use t.area(), can't use pt.area()

usually we use func(r *T) area() int