abstract-factory.md

Abstract Factory Method Pattern

Abstract Factory is a creational design pattern that allows you to create a collection of related objects. It provides an extra level of indirection over the factory design pattern. Using this pattern you can decouple the factory from your client code.

Implementation

The example implementation shows how to create a collection (top & bottom) of summer clothes or winter clothes.

Types

We begin with the simplest interfaces to represent a top or bottom article of clothing. Our items of clothing are Stringer types.

package main

import "fmt"

type Top interface {
	String() string
}

type Bottom interface {
	String() string
}

Next we introduce a couple of tops and bottoms into our system.

type TankTop struct {
}

func (top TankTop) String() string {
	return "Tank Top"
}

type Shorts struct {
}

func (bottom Shorts) String() string {
	return "Shorts"
}

type Sweater struct {
}

func (top Sweater) String() string {
	return "Sweater"
}

type WoolenPant struct {
}

func (bottom WoolenPant) String() string {
	return "Woolen Pant"
}

Next we create an interface to manage the relatedness of clothes (summery or wintery)

type ClothesFactory interface {
	GetTop() Top
	GetBottom() Bottom
}

We give concrete implementations to this interface and bring it all together.

type SummerClothesFactory struct {
}

func (summer SummerClothesFactory) GetTop() Top {
	return TankTop{}
}

func (summer SummerClothesFactory) GetBottom() Bottom {
	return Shorts{}
}

type WinterClothesFactory struct {
}

func (winter WinterClothesFactory) GetTop() Top {
	return Sweater{}
}

func (winter WinterClothesFactory) GetBottom() Bottom {
	return WoolenPant{}
}

Usage

type Wardrobe struct {
	clothesFactory ClothesFactory
}

func NewWardrobe(factory ClothesFactory) *Wardrobe {
	return &Wardrobe{
		clothesFactory: factory,
	}
}

func (wardrobe Wardrobe) GetTop() Top {
	return wardrobe.clothesFactory.GetTop()
}

func (wardrobe Wardrobe) GetBottom() Bottom {
	return wardrobe.clothesFactory.GetBottom()
}


func main() {
	summerWardrobe := NewWardrobe(SummerClothesFactory{})
	fmt.Printf("Summer clothes are %s & %s", summerWardrobe.GetTop(), summerWardrobe.GetBottom())

	fmt.Println()
	winterWardrobe := NewWardrobe(WinterClothesFactory{})
	fmt.Printf("Winter clothes are %s & %s", winterWardrobe.GetTop(), winterWardrobe.GetBottom())

}