设计模式: 细节[装饰模式]

 public abstract class Beverage
    {
        protected string description = "Unknown Description";
        public virtual string getDescription()
        {
            return description;
        }
        public abstract double Cost();
    }
    public class Espresso : Beverage
    {
        public Espresso()
        {
            description = "Espresso";
        }
        public override double Cost()
        {
            return 1.99;
        }
    }
    public class HouseBlend : Beverage
    {
        public HouseBlend()
        {
            description = "Hous eBlend";
        }
        public override double Cost()
        {
            return 0.85;
        }
    }
    public abstract class CondimentDecorator : Beverage
    {
        //public abstract new string getDescription();
    }
    public class Mocha : CondimentDecorator
    {
        Beverage beve;
        public Mocha(Beverage b)
        {
            beve = b;
        }
        public override string getDescription()
        {
            return beve.getDescription() + ",   Mocha";
        }
        public override double Cost()
        {
            return 0.1 + beve.Cost();
        }
    }
    public class Wisp : CondimentDecorator
    {
        Beverage beve;
        public Wisp(Beverage b)
        {
            beve = b;
        }
        public override string getDescription()
        {
            return beve.getDescription() + ",   Wishp";
        }
        public override double Cost()
        {
            return 0.9 + beve.Cost();
        }
    }
    public class test : CondimentDecorator
    {
        //Beverage beve;
        public test()
        {
            //beve = b;
        }
        public override string getDescription()
        {
            //return beve.getDescription() + ",   Wishp";
            return "test";
        }
        public override double Cost()
        {
            //return 0.9 + beve.Cost();
            return 1.1;
        }
    }

以上代码来自 HEAD FIRST ,红色的virtual是原文中没有的, 调料类中的注释也是没有的,相当于,在原文中,基类里面的getDescription函数不是虚函数,在调料类里面抽象化了,

按照JAVA的理解,实际上也没错,毕竟饮料类GetDescription是不需要覆写的,只要把description设置一下就OK了, 调料里面要覆写

但是在C#中运行是有问题的,我猜,C#在发现基类中的GetDescription不是虚方法后,调料类实例化后,调用的Get函数,都是基类的,

所以,为了适应.NET平台,要把基类的get虚拟化,因为virtual不要求子类一定要覆写这个方法,只是说,可以覆写,所以不影响饮料类.

   这里还是感慨一下,细节决定成败啊!