进行虚拟功能仿真

Question

Is there exists some trick to implement virtual functions behaviour in go ? I have the following example.

package main

import "fmt"

type A struct {
}

type B struct {
*A
}

func (this *A) Do() {
    fmt.Println("IM DO")
    this.DoVirtual()
}

func (this *A) DoVirtual() {
    fmt.Println("IM DoVirtual Default implementation")
}

func (this *B) DoVirtual() {
    fmt.Println("IM DoVirtual B implementation")
}

func main() {
    a := &A{}
    a.Do()
    fmt.Println("----")
    b := &B{}
    b.DoVirtual()
    b.Do() // How to make here B.DoVirtual call
}

And the last Do() call uses also default DoVirtual implementation what is actually not was I want. The reason why is it so is go lang iheritance model : this *B and this *A are different pointers in this case, but I wonder is it possible to make some simulation of such behaviour that DoVirtual in last call will be used from B class.

Answer 1

By the time the compiler has selected func (this *A) Do() { the enclosing B is gone, no longer accessible. Go does not support the is-a construct, only the has-a (composition). If one implements a func (this *B) Do() { it will supersede the Do() on *A. Of course, that's not really what you are wanting.

I think the best explanation of the implementation and motivation is here Less is exponentially more from Rob Pike.