Builder Design Pattern
Overview
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Terminology
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Builder UML Diagram
Source Code
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./src/builder/builder-concept.ts
// Builder Concept Sample Code
class Product {
parts: string[] = []
}
interface IBuilder {
buildPartA(): this
buildPartB(): this
buildPartC(): this
getResult(): Product
}
class Builder implements IBuilder {
// The Concrete Builder
product: Product
constructor() {
this.product = new Product()
}
buildPartA() {
this.product.parts.push('a')
return this
}
buildPartB() {
this.product.parts.push('b')
return this
}
buildPartC() {
this.product.parts.push('c')
return this
}
getResult() {
return this.product
}
}
class Director {
// The Director, building a complex representation
static construct() {
'Constructs and returns the final product'
return new Builder()
.buildPartA()
.buildPartB()
.buildPartC()
.getResult()
}
}
// The Client
const PRODUCT1 = Director.construct()
console.log(PRODUCT1.parts)
Output
node ./dist/builder/builder-concept.js
[ 'a', 'b', 'c' ]
Builder Use Case
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Example UML Diagram
Source Code
./src/builder/client.ts
// House Builder Example Code
import IglooDirector from './igloo-director'
import CastleDirector from './castle-director'
import HouseBoatDirector from './houseboat-director'
const IGLOO = IglooDirector.construct()
const CASTLE = CastleDirector.construct()
const HOUSEBOAT = HouseBoatDirector.construct()
console.log(IGLOO.construction())
console.log(CASTLE.construction())
console.log(HOUSEBOAT.construction())
./src/builder/igloo-director.ts
// A Director Class
import House from './house'
import HouseBuilder from './house-builder'
export default class IglooDirector {
static construct(): House {
// Note that in this IglooDirector, it has omitted the
// set_number_of windows call since this Igloo will have
// no windows.
return new HouseBuilder()
.setBuildingType('Igloo')
.setWallMaterial('Ice')
.setNumberDoors(1)
.getResult()
}
}
./src/builder/castle-director.ts
// A Director Class
import House from './house'
import HouseBuilder from './house-builder'
export default class CastleDirector {
static construct(): House {
return new HouseBuilder()
.setBuildingType('Castle')
.setWallMaterial('Sandstone')
.setNumberDoors(100)
.setNumberWindows(200)
.getResult()
}
}
./src/builder/houseboat-director.ts
// A Director Class
import House from './house'
import HouseBuilder from './house-builder'
export default class HouseBoatDirector {
static construct(): House {
return new HouseBuilder()
.setBuildingType('House Boat')
.setWallMaterial('Wood')
.setNumberDoors(6)
.setNumberWindows(8)
.getResult()
}
}
./src/builder/house-builder.ts
import House from './house'
interface IHouseBuilder {
house: House
setBuildingType(buildingType: string): this
setWallMaterial(wallMaterial: string): this
setNumberDoors(number: number): this
setNumberWindows(number: number): this
getResult(): House
}
export default class HouseBuilder implements IHouseBuilder {
house: House
constructor() {
this.house = new House()
}
setBuildingType(buildingType: string): this {
this.house.buildingType = buildingType
return this
}
setWallMaterial(wallMaterial: string): this {
this.house.wallMaterial = wallMaterial
return this
}
setNumberDoors(number: number): this {
this.house.doors = number
return this
}
setNumberWindows(number: number): this {
this.house.windows = number
return this
}
getResult(): House {
return this.house
}
}
./src/builder/house.ts
// The Product
export default class House {
doors = 0
windows = 0
wallMaterial = ''
buildingType = ''
construction(): string {
return `This is a ${this.wallMaterial} ${this.buildingType} with ${this.doors} door(s) and ${this.windows} window(s).`
}
}
Output
node ./dist/builder/client.js
This is a Ice Igloo with 1 door(s) and 0 window(s).
This is a Sandstone Castle with 100 door(s) and 200 window(s).
This is a Wood House Boat with 6 door(s) and 8 window(s).
Summary
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