Method of Golang

This is a creation in Article, where the information may have evolved or changed.

Method

Go does not has classes. However, you can define methods on types.

Package Mainimport ("FMT"    "Math") Type Vertexstruct{X, Y float64}func (v Vertex) Abs () float64 {returnMath. SQRT (v.x*v.x + v.y*v.y)} Func (v*Vertex) Scale (f float64) {v.x= v.x *F v.y= V.y *F}func (v Vertex) Scalevalue (f float64) {v.x= v.x *F v.y= V.y *F}func Main () {V:= vertex{3,4} fmt. Println (V.abs ()) V.scale (2) fmt. Println (V.abs ()) V.scalevalue (2) fmt. Println (V.abs ()) P:= &v P.scale (2) fmt. Println (P.abs ())}

The output is as follows:

5
10
10
20

Three points of note:

1. Methods with pointer receivers can modify the value to which the receiver points.

2. Methods with pointer receivers take either a value or a pointer as the receiver when they is called:

var v Vertexv.scale (5)  // OKP: = &VP. Scale (ten//  OK

3. Methods with value receivers take either a value or a pointer as the receiver when they is called:

var/  OKp: = &//  OK

Interface

Package Mainimport ("FMT") Type IInterface{M ()}type Tstruct{Sstring}func (t*T) M () {fmt. Println (T.S)}func main () {varI i t:= t{"Hello"} i= &T I.M () V:= t{" World"} i=v I.M ()}

The second half of the code in the main function will cause an error: Cannot use V (type T) as type I in assignment:t does not implement I (M method have pointer receiver)

If you change the receiver type of M to value:

Func (T-T) M () {    fmt. Println (T.S)}

The code for the main function will run normally.