装饰者模式的学习（c#）

案例转自https://www.cnblogs.com/stonefeng/p/5679638.html

//主体基类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DecoratorModeDemo
{
   abstract class PanCake
    {
        public string desc = "";
        public abstract string getDesc();
        public abstract double price();
    }
}

//主体：肉夹馍

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DecoratorModeDemo
{
    class Roujiamo:PanCake
    {
        public Roujiamo()
        { this.desc = "肉夹馍"; }

public override string getDesc()
        {
            return desc;
        }

public override double price()
        {
            return 6;
        }

}
}

//主体手抓饼

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DecoratorModeDemo
{
    class TornCake:PanCake
    {
        public TornCake()
        {
            this.desc = "手抓饼";
        }

public override string getDesc()
        {
            return desc;
        }

public override double price()
        {
            return 4;
        }
       
    }
}

//装饰者基类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DecoratorModeDemo
{
   abstract class Condiment:PanCake
    {
        public PanCake panCake;
        public Condiment(PanCake p)
        {
            panCake = p;
        }

}
}

//装饰者煎蛋

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DecoratorModeDemo
{
    class FiredEgg:Condiment
    {
        public FiredEgg(PanCake pancake):base(pancake)
        {
        }
        public override string getDesc()
        {
            return panCake.getDesc()+",煎蛋";
        }
        public override double price()
        {
            return this.panCake.price() + 2;
        }
    }
}

//主函数

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DecoratorModeDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            TornCake torncake = new TornCake();
            Console.WriteLine(torncake.getDesc() + " ￥" +torncake.price().ToString());

PanCake roujiamo = new Roujiamo();
            roujiamo = new FiredEgg(roujiamo);
            roujiamo = new FiredEgg(roujiamo);
            Console.WriteLine(roujiamo.getDesc()+" ￥"+roujiamo.price());
            Console.ReadLine();
           
        }
    }
}

运行结果

心得：装饰者派生自主体基类，继承了主体需要操作的对象。同时装饰者的成员对象中有主体，用以耦合主体。通过创建不同的装饰者派生类，重写主体类方法来实现对主体类的不同操作。

roujiamo = new FiredEgg(roujiamo)实际上roujiamo已经变成了煎蛋，只不过这个煎蛋的成员包含肉夹馍，返回的方法经重写已经用原肉夹馍处理过了。