Factory Design Pattern
Overview
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Terminology
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Factory UML Diagram
Source Code
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./src/factory/factory-concept.ts
// The Factory Concept
interface IProduct {
name: string
createObject(): this
}
class ConcreteProduct implements IProduct {
name = ''
createObject() {
return this
}
}
class ConcreteProductA extends ConcreteProduct {
constructor() {
super()
this.name = 'ConcreteProductA'
}
}
class ConcreteProductB extends ConcreteProduct {
constructor() {
super()
this.name = 'ConcreteProductB'
}
}
class ConcreteProductC extends ConcreteProduct {
constructor() {
super()
this.name = 'ConcreteProductC'
}
}
class Creator {
static createObject(someProperty: string): IProduct {
if (someProperty === 'a') {
return new ConcreteProductA()
} else if (someProperty === 'b') {
return new ConcreteProductB()
} else {
return new ConcreteProductC()
}
}
}
// The Client
const PRODUCT = Creator.createObject('b')
console.log(PRODUCT.name)
Output
node ./dist/factory/factory-concept.js
ConcreteProductB
Factory Use Case
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Factory Example UML Diagram
Source Code
./src/factory/client.ts
// Factory Use Case Example Code
import ChairFactory from './chair-factory'
const CHAIR = ChairFactory.getChair('SmallChair')
console.log(CHAIR.getDimensions())
./src/factory/dimension.ts
export type dimension = {
height: number
width: number
depth: number
}
./src/factory/chair.ts
import { dimension } from './dimension'
// A Chair Interface
interface IChair {
height: number
width: number
depth: number
getDimensions(): dimension
}
// The Chair Base Class
export default class Chair implements IChair {
height = 0
width = 0
depth = 0
createObject(): IChair {
return this
}
getDimensions(): dimension {
return {
width: this.width,
depth: this.depth,
height: this.height,
}
}
}
./src/factory/chair-factory.ts
import SmallChair from './small-chair'
import MediumChair from './medium-chair'
import BigChair from './big-chair'
import IChair from './chair'
export default class ChairFactory {
static getChair(chair: string): IChair {
if (chair == 'BigChair') {
return new BigChair()
} else if (chair == 'MediumChair') {
return new MediumChair()
} else {
return new SmallChair()
}
}
}
./src/factory/small-chair.ts
import Chair from './chair'
export default class SmallChair extends Chair {
constructor() {
super()
this.height = 40
this.width = 40
this.depth = 40
}
}
./src/factory/medium-chair.ts
import Chair from './chair'
export default class MediumChair extends Chair {
constructor() {
super()
this.height = 60
this.width = 60
this.depth = 60
}
}
./src/factory/big-chair.ts
import Chair from './chair'
export default class BigChair extends Chair {
constructor() {
super()
this.height = 80
this.width = 80
this.depth = 80
}
}
Output
node ./dist/factory/client.js
{'width': 40, 'depth': 40, 'height': 40}
Summary
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