装饰模式

定义

即在不改变类本身,动态地扩展对象的功能。它是通过创建一个包装对象,也就是装饰来包裹真实的对象。包装对象和原对象拥有相似的接口方法(功能)。

举例

类图

代码

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public class OrderInfo
   {
       /// <summary>
       /// 下单时间
       /// </summary>
       public DateTime CreateTime{get;set;}
       /// <summary>
       /// 等级
       /// </summary>
       public int Level{get;set;}
   }
   public abstract class OrderManager
   {
       public abstract void Summit(OrderInfo order);
       public abstract void CancelOrder(OrderInfo order);
   }
 
   public class SimpleOrderManager : OrderManager
   {
 
       public override void Summit(OrderInfo order)
       {
           //TODO summit the order
           Console.WriteLine("Summit the order");
       }
 
       public override void CancelOrder(OrderInfo order)
       {
           //TODO cancel the order
           Console.WriteLine("cancel the order");
       }
   }
   /// <summary>
   ///
   /// </summary>
   public class OrderManagerDecorator : OrderManager
   {
       private OrderManager orderManager = null;
       public  OrderManagerDecorator(OrderManager orderManager)
       {
           this.orderManager = orderManager;
       }
       public override void Summit(OrderInfo order)
       {
           orderManager.Summit(order);
       }
 
       public override void CancelOrder(OrderInfo order)
       {
           orderManager.CancelOrder(order);
       }
   }
 
   public class ForeignOrderManager : OrderManagerDecorator
   {
       public ForeignOrderManager(OrderManager orderManager):base(orderManager)
       {
       }
       public override void Summit(OrderInfo order)
       {
           if (ValidateOrder(order))
           {
               base.Summit(order);
           }
           else
           {
               throw new Exception("the level of the order is disable");
           }
       }
       public bool ValidateOrder(OrderInfo order)
       {
           //TODO validate the order
           bool result = order.Level > 2;
           return result;
       }
       public override void CancelOrder(OrderInfo order)
       {
           base.CancelOrder(order);
       }
   }
   public class SuperOrderManager : OrderManagerDecorator
   {
       public SuperOrderManager(OrderManager orderManager)
           : base(orderManager)
       {
       }
       public override void Summit(OrderInfo order)
       {
          base.Summit(order);
       }
       
       public override void CancelOrder(OrderInfo order)
       {
           base.CancelOrder(order);
       }
       private bool CheckOrder(OrderInfo order)
       {
 
           if (order.CreateTime.AddDays(3) < DateTime.Now)
           {
               return false;
           }
           else
           {
               return true;
           }
            
       }
   }

  

 

总结

曾经以为装饰模式和组合模式很像!只是因为他们他们都包含需要包装的对象。而后来想想,才知道他们本质上差别很大:组合模式在于组合,是多个对象组合成合成的对象,合成对象可以去触发控制其包含的对象。装饰者模式则是对类本身功能的扩展,从代码上看,他是包含单个包装对象。

在编程中非常经典的使用就是Stream类型对象的构造了。主要包括FileSteam,BufferdStream等。

最后在画一幅图说明装饰模式调用的样式------实现装饰功能本身的扩展

 

posted @   Tim_et  阅读(220)  评论(0编辑  收藏  举报
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