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Factory Pattern : Factory Method, Abstract Factory, Factory Pattern in Swfit

07 May 2019 |  

Factory Pattern :factory:

The factory pattern is a way to encapsulate the implementation details of creating objects, which adheres to a common base class or interface.

객체 생성을 전담하는 struct/class를 만들어 구체적인 생성과정을 그 안에 구현하는 패턴

객체 생성을 다른 struct/class이 전담한다.

 

  • 목적

    • 객체 생성을 위한 복잡한 과정을 없애기 위함

      (사실상 없애는게 아니라 겉으로 드러나지 않도록 캡슐화해서 사용하도록 함)

    • 객체 생성의 구체적인 구현을 generic하게 객체를 사용하여 분리한다.

  • 이럴 때 사용한다

    • 만들 객체의 클래스 종류를 예측할 수 없을 때
    • 만들어야 할 객체의 하위 클래스를 명시하고 싶을 때

  • 종류

    • Factory Method Pattern
    • Abstract Factory Pattern

 

📌 Table Of Contents

  • Factory Metod Pattern
  • Abstract Factory Pattern
  • 공통점 & 차이점
  • Cf) Design Pattern
  • Factory Pattern in Swift

 

 

Factory Method Pattern

한 객체(상품)만 생산함

Factory method는 단일 상품 생산

Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.

  • CoordinateCalculator 에서 사용한 방법

  • factory method 1개

  • example

    • Product

      // product 추상 클래스
public abstract class Shoes {
  public abstract String getName();
}
    
// concrete product 
public abstract class NikeShoes extends Shoes {
  @Override
  public String getName() {
    return "Nike";
  }
}
    
public abstract class PumaShoes extends Shoes {
  @Override
  public String getName() {
    return "Puma";
  }
}
    
// product 추상 클래스 Tshirt
public abstract class Tshirt {
  public abstract String getName();
}
    
// concrete product 
public abstract class NikeTshirt extends Tshirt {
  @Override
  public String getName() {
    return "Nike";
  }
}
    
public abstract class PumaTshirt extends Tshirt {
  @Override
  public String getName() {
    return "Puma";
  }
}

    • Factory

      // Factory 추상 클래스
public abstract class ShoesFactory {
  public abstract Shoes createShoes(String type);
}
    
public class BrandShoesFactory extends ShoesFactory {
  @Override
  public abstract Shoes createShoes(String type) {
    Shoes shoes = null;
        
    switch(type) {
        case("Nike")
          shoes = new NikeShoes();
          break;
        case("Puma")
          shoes = new PumaShoes();
          break;
    }
        
    return shoes;
  }
}
    
public abstract class TshirtFactory {
  public abstract Tshirt createTshirt(String type);
}
    
public class BrandTshirtFactory extends TshirtFactory {
  @Override
  public abstract Tshirt createTshirt(String type) {
    Tshirt tshirt = null;
        
    switch(type) {
        case("Nike")
          tshirt = new NikeTshirt();
          break;
        case("Puma")
          tshirt = new PumaTshirt();
          break;
    }
        
    return shoes;
  }
}

    • Sportsware Factory

      public class SportswareFactory {
  public void createSportsware(String type) {
    ShoesFactory shoesFactory = new BrandShoesFactory();
    TshirtFactory tshirtFactory = new BrandTshirtFactory();
          
    shoesFactory.createShoes(type);
    tshirtFactory.createTshirt(type);
  }
}

    • Client

      public class Client {
  public static void main(String args[]) {
    SportswareFactory factory = new SportswareFactory();
    factory.createSportsware("Nike");
  }
}

 

 

Abstract Factory Pattern

관련된 상품들 여러 개를 생산함

단일 상품을 생산하는 여러 개 factory method를 가진 abstract factory. 상품들은 서로 관련된 family

Provide an interface for creating families of related or dependent objects without specifying their concrete classes.

  • 관련된 객체들을 한꺼번에 캡슐화 하여 팩토리로 만들어서 일관되게 객체를 생성하도록 한다.

  • factory method 여러 개

  • 관련된 객체들을 각각 make()(create)

  • example

    • Product - shoes, tshirt

      // product 추상 클래스 Shoes
public abstract class Shoes {
  public abstract String getName();
}
    
// concrete product 
public abstract class NikeShoes extends Shoes {
  @Override
  public String getName() {
    return "Nike";
  }
}
    
public abstract class PumaShoes extends Shoes {
  @Override
  public String getName() {
    return "Puma";
  }
}
    
// product 추상 클래스 Tshirt
public abstract class Tshirt {
  public abstract String getName();
}
    
// concrete product 
public abstract class NikeTshirt extends Tshirt {
  @Override
  public String getName() {
    return "Nike";
  }
}
    
public abstract class PumaTshirt extends Tshirt {
  @Override
  public String getName() {
    return "Puma";
  }
}

    • Factory interface

      public interface SportswareFactory {
  public Shoes createShoes();
  public Tshirt createTshirt();
}
    
public class NikeFactory implements SportswareFactory {
  @Override
  public Shoes createShoes() {
    return new NikeShoes();
  }
  @Override
  public Tshirt createTshirt() {
    return new NikeTshirt();
  }
}
    
public class PumaFactory implements SportswareFactory {
  @Override
  public Shoes createShoes() {
    return new PumaShoes();
  }
  @Override
  public Tshirt createTshirt() {
    return new PumaTshirt();
  }
}

    • Factory of Factory

      public class SportswareFactoryCreator {
  public void createSportswareFactoryOf(String type) {
    SportswareFactory factory = null;
        
    switch(type) {
      case "Nike":
        factory = new NikeFactory();
        break;
      case "Puma":
        factory = new PumaFactory();
        break;
    }
        
    factory.createShoes();
    factory.createTshirt();
  } 
}

    • Client

      public class Client {
	public static void main(String args[]) {
    SportswareFactoryCreator factoryCreator = new SportswareFactoryCreator();
    factoryCreator.createSportswareFactoryOf("Puma");
  }
}

 

 

공통점 & 차이점

공통점

  1. 구조: factory, product 가 필요함
    • Factory(Creator) : 객체 종류를 판단하고 생성
    • Product : Factory에서 생성되는 객체의 공통 조상. Factory에서 생성되는 객체는 product를 상속받거나, 채택한 type이다.
  2. 생성을 factory 에서 맡아서 함 - factory method에서 객체 생성 담당
    • factory method 인자에 따라 생성되는 객체가 결정된다.
  3. 실제 구현대상인 concreate class/struct와 client 간의 결합도를 낮춘다.

 

차이점

  Factory Method Abstract Factory
생성범위 한 Factory에 make() 한 개 한 Factory 당, 연관된 여러 종류(개)의 make() 지원
객체 종류 결정 인자에 따라 객체 종류가 결정됨 인자에 따라 객체 생성을 담당하는 Factory의 종류가 결정됨
결합도 낮추는 대상 ConcreteProduct & Client ConcreteFactory & Client
Focus factory method 레벨에 집중 Abstract Factory 레벨에 집중
추상화 level method class

참조

:paperclip: Factory Method Pattern

factory method

 

:paperclip: Abstract Factory Pattern

Abstract Factory

 

 

:mag: cf) Design Pattern

Design patterns are blueprints which outline the best practices that create re-usable object oriented code, solving common software problems.

  • best practice(모범사례) to solve sw problem

  • Software Design Pattern - 크게 4가지로 구분된다 (참조)
  • Creational Pattern : Factory Pattern이 소속된 카테고리
    • 객체 생성의 복잡도를 낮추는 모든 것을 다룬다.

 

 

Factory Pattern in Swift

  • Protocol 사용 : Product 공통 조상 type으로 사용. 자격의 의미로 좀 더 유연하게 사용 가능

  • Naming : swift api guidline - 팩토리 메소드 이름은 “make”로 시작하라. 예시) x.makeIterator()

  • ex. Payable protocol & Card Factory

struct CardOwner {
    let name: String
    let cardtype: CardType
    
    enum CardType {
        case check, credit, prepaid
    }
}

protocol Payable {
    func pay()
}

struct CheckCard: Payable {
    let owner: CardOwner
    func pay() {
        print("\(owner.name) pays with check card")
    }
}

struct CreditCard: Payable {
    let owner: CardOwner
    func pay() {
        print("\(owner.name) pays with credit card")
    }
}

struct PrepaidCard: Payable {
    let owner: CardOwner
    func pay() {
        print("\(owner.name) pays with prepaid card")
    }
}

struct CardFactory {
    static func makeCard(for owner: CardOwner) -> Payable {
        switch owner.cardtype {
        case .check:
            return CheckCard(owner: owner)
        case .credit:
            return CreditCard(owner: owner)
        case .prepaid:
            return PrepaidCard(owner: owner)
        }
    }
}

let newCard = CardFactory.makeCard(for: CardOwner(name: "Diana", cardtype: .check))
newCard.pay()

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