Core Design Patterns(1) Decorator 装饰模式

VS 2008

当我们需要给一个已有的对象动态的附加状态或行为时，使用装饰模式。
装饰模式的要点是：装饰类实现了最初的被装饰类，并且包含了被装饰类的一个实例

1. 模式静态类图



2. 应用

    从一只可以写的Pen开始
    把它装饰成有颜色的笔、粗线的笔，甚至可以是有颜色且粗线的笔



IWritable

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

namespace DesignPattern.Decorator.BLL {
    interface IWritable {
        void Write();
    }
}

Pen

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

namespace DesignPattern.Decorator.BLL {
    class Pen : IWritable {
        IWritable Members#region IWritable Members

        public void Write() {
            Console.WriteLine("I can write!");
        }

        #endregion
    }
}

ColoredPen

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

namespace DesignPattern.Decorator.BLL {
    class ColoredPen : IWritable {

        IWritable component = null;
        string color = string.Empty;

        public ColoredPen(IWritable component, string color) {
            this.component = component;
            this.color = color;
        }

        IWritable Members#region IWritable Members

        public void Write() {
            this.component.Write();
            Console.WriteLine("my color is " + color);
        }

        #endregion

        public void SetColor(string color) {
            this.color = color;
        }
    }
}

BoldPen

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

namespace DesignPattern.Decorator.BLL {
    class BoldPen : IWritable {

        IWritable component = null;
        int borderWidth = 0;

        public BoldPen(IWritable component, int borderWidth) {
            this.component = component;
            this.borderWidth = borderWidth;
        }

        IWritable Members#region IWritable Members

        public void Write() {
            this.component.Write();
            Console.WriteLine("my border width is " + this.borderWidth.ToString()); 
        }

        #endregion

        public void SetBorderWidth(int borderWidth) {
            this.borderWidth = borderWidth;
        }
    }
}

Client

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using DesignPattern.Decorator.BLL;

namespace DesignPattern.Decorator {
    class Program {
        static void Main(string[] args) {
            IWritable p = new Pen();
            p.Write();
            Console.WriteLine();

            ColoredPen coloredPen = new ColoredPen(p, "red");
            coloredPen.Write();
            Console.WriteLine();

            BoldPen boldPen = new BoldPen(p, 2);
            boldPen.Write();
            Console.WriteLine();

            BoldPen coloredAndBoldPen = new BoldPen(coloredPen, 4);
            coloredAndBoldPen.Write();
        }
    }
}