Factory method pattern - DeanHristov/ts-design-patterns-cheat-sheet GitHub Wiki

A Factory Method is a creational design pattern that provides an interface for creating objects in a superclass but allows subclasses to alter the type of objects that will be created. A simple UML diagram can be seen here.

A Great fit when:

• When we don’t know beforehand the exact types and dependencies of the objects with which the code should work.
• When we want to save resources by reusing existing objects instead of rebuilding them each time.

Example:

Public contract

// Product type
interface IBurger {
  burgerName: string;
}

The creator class

abstract class ChefCreator {
  cookBurger() {
    return this.factoryMethod();
  }

  protected abstract factoryMethod(): Burger;
}

A concrete creator 1

class AmericanChef extends ChefCreator {
  protected factoryMethod(): IBurger {
    return new BeefBurger('BeefBurger');
  }
}

A concrete creator 2

class ItalyChef extends ChefCreator {
  protected factoryMethod(): IBurger {
    return new VeggieBurger('VeggieBurger');
  }
}

A concrete product 1

class BeefBurger implements IBurger {
  burgerName: string;

  constructor(burgerName: string) {
    this.burgerName = burgerName;
  }
}

A concrete product 2

class VeggieBurger implements IBurger {
  burgerName: string;

  constructor(burgerName: string) {
    this.burgerName = burgerName;
  }
}

Code in action

const italyChef: ItalyChef = new ItalyChef();
const americanChef: AmericanChef = new AmericanChef();

const veggieBurger: IBurger = italyChef.cookBurger();
const beefBurger: IBurger = americanChef.cookBurger();

console.log(beefBurger); // { burgerName: 'BeefBurger' }
console.log(veggieBurger); // { burgerName: 'VeggieBurger' }

More info can be found on the wiki page.