[Go] Builder pattern demo.

package main

import (
    "fmt"
)

type IAnimal interface {
    Speak()
}

type AnimalType int

const (
    Duck AnimalType = iota
    Dog
    Tiger
)

type DuckClass struct{}

func NewDuck() *DuckClass {
    return new(DuckClass)
}

func (d *DuckClass) Speak() {
    fmt.Println("Pack pack")
}

type DogClass struct{}

func NewDog() *DogClass {
    return new(DogClass)
}

func (d *DogClass) Speak() {
    fmt.Println("Wow wow")
}

type TigerClass struct{}

func NewTiger() *TigerClass {
    return new(TigerClass)
}

func (t *TigerClass) Speak() {
    fmt.Println("Halum halum")
}

func New(t AnimalType) IAnimal {
    switch t {
    case Duck:
        return NewDuck()
    case Dog:
        return NewDog()
    case Tiger:
        return NewTiger()
    default:
        panic("Unknown animal type")
    }
}

func main() {
    animals := make([]IAnimal, 0)

    duck := New(Duck)
    dog := New(Dog)
    tiger := New(Tiger)

    animals = append(animals, duck, dog, tiger)

    for _, a := range animals {
        a.Speak()
    }
}