模式定義

工廠方法模式(Factory Method Pattern)又稱為工廠模式，也叫虛擬構造器(Virtual Constructor)模式或者多態工廠(Polymorphic Factory)模式，它屬於類創建型模式。在工廠方法模式中，工廠父類負責定義創建產品對象的公共接口，而工廠子類則負責生成具體的產品對象，這樣做的目的是將產品類的實例化操作延遲到工廠子類中完成，即通過工廠子類來確定究竟應該實例化哪一個具體產品類。

UML類圖

• Product 抽象產品
• ConcreteProduct 具體產品
• Factory 抽象工廠

• ConcreteFactory 具體工廠

  代碼結構組成

  public  class FactoryApp
  {
      public static void Run()
      {
          Creator[] creators = new Creator[2];
  
          creators[0] = new ConcreteCreatorA();
          creators[1] = new ConcreteCreatorB();
  
          foreach(Creator creator in creators)
          {
              Product product = creator.FactoryMothed();
              Console.WriteLine("Created {0}", product.GetType().Name);
          }
      }
  }
  
  public class Product
  { }
  public class ConcreteProductA:Product
  { }
  public class ConcreteProductB:Product
  { }
  
  public abstract class Creator
  {
      public abstract Product FactoryMothed();
  }
  
  public class ConcreteCreatorA:Creator
  {
      public override Product FactoryMothed()
      {
          return new ConcreteProductA();
      }
  }
  
  public class ConcreteCreatorB:Creator
  {
      public override Product FactoryMothed()
      {
          return new ConcreteProductB();
      }
  }
   
  

  情景案例

  以麥當勞的漢堡為例，假設漢堡有兩種牛肉堡和雞肉堡，不同的漢堡有不同的漢堡廚師制作。
  可能有疑問：為是麽是有工廠設計模式呢，反而多個多類更麻煩？
  
• 重寫大量重復代碼： 如果創建廚師類需要復雜的過程，比如驗證廚藝水平等等，並不是簡單通過new就能完成，那麽將這些驗證放入工廠會減少重寫大量重復代碼

• 容易擴展： 如果再家一個芝士堡只需添加芝士堡類與芝士堡廚師類，滿足開閉原則

  public class FactoryApp
  {
      public static void Run()
      {
          BurgerCook[] burgerCook = new BurgerCook[2];
  
          burgerCook[0] = new BeefBurgerCook();
          burgerCook[1] = new ChickenBurgerCook();
  
          foreach (BurgerCook cook in burgerCook)
          {
              Burger burger = cook.MarkBurger();
              Console.WriteLine("Created {0}", burger.GetType().Name);
          }
      }
  }
  
  public class Burger
  { }
  public class BeefBurger : Burger
  { }
  public class ChickenBurger : Burger
  { }
  
  public abstract class BurgerCook
  {
      public abstract Burger MarkBurger();
  }
  
  public class BeefBurgerCook : BurgerCook
  {
      public override Burger MarkBurger()
      {
          return new BeefBurger();
      }
  }
  
  public class ChickenBurgerCook : BurgerCook
  {
      public override Burger MarkBurger()
      {
          return new ChickenBurger();
      }
  }
   
  

工廠模式（Factory Method Pattern）