设计模式示例二　Decorator(装饰者)

示例名称:超级递送员
示例说明:定义基类(BaseDelivery)和虚方法(Deliver),定义继承自该基类的三个子类(MilkDelivery、NewspaperDelivery和CarDelivery),重写基类的虚方法(Deliver)。
示例类图:



关键部分说明

BaseDelivery



using System;




namespace Delivery




...{


public class BaseDelivery




...{


public virtual void Deliver()




...{


Console.WriteLine("我是早晨的送递员");


}


}


}


Deliver是虚方法，子类需要重写它。

MilkDelivery、NewspaperDelivery和CarDelivery



using System;




namespace Delivery




...{


public class MilkDelivery : BaseDelivery




...{


private BaseDelivery _delivery;




public MilkDelivery(BaseDelivery delivery)




...{


_delivery = delivery;


}




public override void Deliver()




...{


_delivery.Deliver();


Console.WriteLine("我送来牛奶！");


}


}


}






using System;




namespace Delivery




...{


public class NewspaperDelivery : BaseDelivery




...{


private BaseDelivery _delivery;


public NewspaperDelivery(BaseDelivery delivery)




...{


_delivery = delivery;


}


public override void Deliver()




...{


_delivery.Deliver();


Console.WriteLine("我送来了报纸！");


}


}


}






using System;




namespace Delivery




...{


public class CarDelivery:BaseDelivery




...{


private BaseDelivery _delivery;


public CarDelivery(BaseDelivery delivery)




...{


_delivery = delivery;


}


public override void Deliver()




...{


_delivery.Deliver();


Console.WriteLine("我还送来了你买的小汽车，梦想成真了吧，哈哈!");


}


}


}



这三个类分别继承了BaseDelivery(is a的关系)，含有一个BaseDelivery类型的私有字段和一个BaseDelivery参数的构造方法，重写父类BaseDelivery的Deliver方法。

应用



using System;


using System.Collections.Generic;


using System.Text;




namespace Delivery




...{


class Program




...{


static void Main(string[] args)




...{


BaseDelivery baseDelivery = new BaseDelivery();


MilkDelivery milkDelivery = new MilkDelivery(baseDelivery);


NewspaperDelivery newsDelivery = new NewspaperDelivery(milkDelivery);


CarDelivery carDelivery = new CarDelivery(newsDelivery);


carDelivery.Deliver();


Console.Read();


}


}


}


任何继承了BaseDelivery的子类都可以做为其它子类的构造函数的参数传递。即可实现对该子类的装饰(Decorator)。

运行结果



现在是不是很开心！