Design Pattern : Factory工廠模式 (泛型)

Design Pattern : Factory工廠模式 (泛型)

藉由使用Interface和工廠模式，可以讓工廠類別(Factory Class)去做建立物件的細節，至於使用者只要使用Factory去建立需要的物件，不需要知道物件怎麼建立的，或是細節 ~ 來降低耦合性。

底下列出三種建立Factory的方法：

■     Normal Factory

■     Static Factory

■     Override Abstract Factory

1.  首先我們先建立一個Interface：ICar， 然後實作了三個Class … Focus, Civic, V60 (這邊只列出一個)

interface ICar
{
  Color Color { get; set; }
  String Name { get; set; }
  void Drive();
}

class Focus:ICar
{
   private Color color;
   private String name;// = typeof(Focus).Name;
   private const String BRAND = "FORD";
   public Focus()
   {
     //取得當前類別名稱
     name = System.Reflection.MethodBase.GetCurrentMethod().DeclaringType.Name;
   }

   public Color Color
   {
      get { return color; }
      set { color = value; }
   }
   public String Name
   {
      get { return name; }
      set { name = value; }
   }
   public void Drive()
   {
     Console.WriteLine("I am driving {0} {1} ({2})", color.ToString(), name, BRAND);
   }
}

2.  Normal Factory
static class CarFactoryNormal
{
   public static ICar Create<T>() where T:ICar
   {
      ICar createCar;
      switch(typeof(T).Name.ToString())
      {
         case "Focus":
             createCar = new Focus();
             break;
         case "Civic":
             createCar = new Civic();
             break;
         case "V60":
             createCar = new V60();
             break;
         default:
             createCar = null;
             break;
      }
      return createCar as ICar;
   }
}

使用方式：
ICar _focus = CarFactoryNormal.Create<Focus>();
_focus.Color = Color.Silver;
_focus.Drive();

3.      Static Factory
非常簡潔明瞭的方式~~

/// <typeparam name="F">Interface</typeparam>
/// <typeparam name="T">Class</typeparam>
public static class CarFactoryStatic<F,T> where T:F, new()
{
  public static F Create()
  {
    return new T();
  }
}

使用方式：
ICar _focus = CarFactoryStatic<ICar, Focus>.Create();
_focus.Color = Color.Silver;
_focus.Drive();

4.  Override Abstract Factory
利用Abstract和Override，可以建立更多客製化的Factory，比如下面會在建立ICar物件前，先顯示一段訊息（灰底部分）。

/// Abstract Factory class
public abstract class AbstractFactory<F,T> where T:F, new()
{
   public abstract F Create();
}

/// Factory class
public class CarFactory<F,T> : AbstractFactory<F,T> where T:F, new()
{
  public override F Create()
  {
    Console.WriteLine("Use Abstract Factory method...");
    return new T();
  }
}

使用方式：
CarFactory<ICar, Focus> Factory1 = new CarFactory<ICar, Focus>();
ICar _focus = Factory1.Create();
_focus.Color = Color.Silver;
_focus.Drive();

5.       顯示結果

1.測試一般Factory方法
I am driving Silver Focus (FORD)

2.測試靜態Factory的方法
I am driving Silver Focus (FORD)

3.測試覆寫Abstract Factory的方法

Use Abstract Factory method...

I am driving Silver Focus (FORD)

6.      End