入门：在struct上调用方法和在指向该struct的指针上调用方法之间有什么区别？

Supoose that I have a Vertex type

type Vertex struct {
    X, Y float64
}

and I've defined a method

func (v *Vertex) Abs() float64 {
    return math.Sqrt(v.X*v.X + v.Y*v.Y)
}

What's the difference between those two calls ? (both of them return the same result)

v1 := Vertex{3, 4}
fmt.Println(v1.Abs())

v2 := &Vertex{3, 4}
fmt.Println(v2.Abs())

The first version is the equivalent of

var v1 Vertex
v1.X = 3
v1.y = 4
fmt.Println((&v1).Abs)

The second version is the equivalent of

var v2 *Vertex
v2 = new(Vertex)
v2.X = 3
v2.y = 4
fmt.Println(v2.Abs)

So the only substantial difference is that v1 is a value and v2 is a pointer to a value of type Vertex.