CSharp设计模式读书笔记（10）：装饰模式(学习难度：★★★☆☆，使用频率：★★★☆☆)

装饰模式(Decorator Pattern)：

动态地给一个对象增加一些额外的职责，就增加对象功能来说，装饰模式比生成子类实现更为灵活。

模式角色与结构：

示例代码：

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

namespace CSharp.DesignPattern.DecoratorPattern
{
    class Program
    {
        static void Main(string[] args)
        {
            Component component;
            Component componentDecorator;

            component = new Window();
            componentDecorator = new ScrollBarDecorator(component);

            componentDecorator.display();

            component = new TextBox();
            componentDecorator = new BlackBorderDecorator(component);

            componentDecorator.display();

            Console.ReadLine();
        }
    }

    // 抽象构件
    abstract class Component
    {
        public abstract void display();
    }

    // 具体构件
    class Window : Component
    {
        public override void display()
        {
            Console.WriteLine("Window...");
        }
    }

    class TextBox : Component
    {
        public override void display()
        {
            Console.WriteLine("TextBox...");
        }
    }

    // 抽象装饰类
    class ComponentDecorator : Component
    {
        private Component component; // 维持对抽象构件类型对象的引用

        public ComponentDecorator(Component component) // 注入抽象构件类型的对象
        {
            this.component = component;
        }

        public override void display()
        {
            component.display();
        }
    }

    // 具体装饰类
    class ScrollBarDecorator : ComponentDecorator
    {
        public ScrollBarDecorator(Component component) 
            : base(component)
        {   
        }

        public override void display()
        {
            this.SetScrollBar();
            base.display();
        }

        public void SetScrollBar()
        {
            Console.WriteLine("Add Scroll Bar...");
        }
    }

    class BlackBorderDecorator : ComponentDecorator
    {
        public BlackBorderDecorator(Component component)
            : base(component)
        { }

        public override void display()
        {
            this.SetBlackBorder();
            base.display();
        }

        public void SetBlackBorder()
        {
            Console.WriteLine("Add Black Border...");
        }
    }
}