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！