Visitor Pattern in Golang

visitor_pattern_in_go.go

package main
//Thanks to http://ecs.victoria.ac.nz/foswiki/pub/Main/TechnicalReportSeries/ECSTR11-01.pdf

import (
    "fmt"
)

//We will have multiple car parts
type CarPart interface {
    Accept(CarPartVisitor)
}

type Wheel struct {
    Name string
}

func (this *Wheel) Accept(visitor CarPartVisitor) {
    visitor.visitWheel(this)
}

type Engine struct {}

func (this *Engine) Accept(visitor CarPartVisitor) {
    visitor.visitEngine(this)
}

type Car struct {
    parts []CarPart
}

func NewCar() *Car {
    this := new(Car)
    this.parts = []CarPart{
        &Wheel{"front left"},
        &Wheel{"front right"},
        &Wheel{"rear right"},
        &Wheel{"rear left"},
        &Engine{}}
    return this
}

func (this *Car) Accept(visitor CarPartVisitor) {
    for _, part := range this.parts {
        part.Accept(visitor)
    }
}

//Interface of the visitor
type CarPartVisitor interface {
    visitWheel(wheel *Wheel)
    visitEngine(engine *Engine)
}

//Concrete Implementation of the visitor
type GetMessageVisitor struct{
    Messages []string
}

func (this *GetMessageVisitor) visitWheel(wheel *Wheel) {
    this.Messages = append(this.Messages, fmt.Sprintf("Visiting the %v wheel\n", wheel.Name))
}

func (this *GetMessageVisitor) visitEngine(engine *Engine) {
    this.Messages = append(this.Messages, fmt.Sprintf("Visiting engine\n"))
}

//Usage of the visitor
func main() {
    car := NewCar()
    visitor := new(GetMessageVisitor)
    car.Accept(visitor)
    fmt.Println(visitor.Messages)
}