gistfile1.go

package main

import "fmt"

type NamedVisitor struct {
    onNormalName func(NormalName)
    onFullName func(FullName)
}

type Named interface {
    name() string
    accept(visitor *NamedVisitor)
}

type NormalName struct {
    firstName string
    lastName string
}

type FullName struct {
    firstName string
    middleName string
    lastName string
}

func (p NormalName) name() string {
     return p.firstName + " " + p.lastName
}

func (p FullName) name() string {
     return p.firstName + " " + p.middleName + " " + p.lastName
}

func (p NormalName) accept(visitor *NamedVisitor) {
    visitor.onNormalName(p)
}

func (p FullName) accept(visitor *NamedVisitor) {
    visitor.onFullName(p)
}

func NewNamedVisitor(onNormalName func(NormalName), onFullName func(FullName)) *NamedVisitor {
    visitor := new(NamedVisitor)
    visitor.onNormalName = onNormalName
    visitor.onFullName = onFullName
    return visitor
}

func main() {
    names := []Named{}

    name1 := NormalName{"Foo", "Bar"}
    names = append(names, name1)

    name2 := FullName{"Foo", "Bar", "Baz"}
    names = append(names, name2)

    for _, p := range names {
        fmt.Println(p.name())
    }

    visitor := NewNamedVisitor(
        func(name NormalName) { fmt.Println("Normal name") },
        func(name FullName) { fmt.Println("Full name") } )

    for _, p := range names {
        p.accept(visitor)
    }
}