桥接模式 (Bridge Pattern)-结构型模式第五篇

最近换了一份新工作，全新的开始，一切还在奋斗的道路上，自己给自己打个气!

设计模式系列很久没有更新了，废话不多说，开始今天的桥接模式。

定义：

何为Bridge模式？我们知道，实现与抽象之间总是存在着强依赖，Bridge模式的意义就是解耦实现与抽象，这意味着实现与抽象不再有着静态的依赖关系，它们彼此可以拥有独立的变化，从而互不影响。

UML：

实例：

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

namespace BridgePattern
{

    /// <summary>
    /// This is abstraction, represents shape.
    /// </summary>
    public interface IShape
    {
        /// <summary>
        /// The shape has a property called Drawing, which represents implemention of drawing behavior.
        /// </summary>
        IDrawing Drawing { get; set; }
        /// <summary>
        /// The shape has a method called Draw. If you don't adopt Bridge pattern, in general, you should implement this method to draw.
        /// </summary>
        /// <returns></returns>
        string Draw();
    }

    /// <summary>
    /// This is a concrete abstraction. represents circle shape.
    /// </summary>
    public class CircleShape : IShape
    {
        public CircleShape(IDrawing drawing)
        {
            Drawing = drawing;
        }
        public IDrawing Drawing { get; set; }
        /// <summary>
        /// The method Draw uses IDrawing to bridge. You will find that you don't need to implement concrete darwing behavior, you just forward the request to IDrawing.  
        /// </summary>
        /// <returns></returns>
        public string Draw()
        {
            return Drawing.Draw();
        }
    }

    /// <summary>
    /// This is abstraction of implementation, represents abstract implementation, it has ability to independent with IShape.
    /// </summary>

    public interface IDrawing
    {
        string Draw();
    }

    /// <summary>
    /// This is concrete implementation, derived from IDrawing.
    /// </summary>
    public class CircleDrawing : IDrawing
    {
        public string Draw()
        {
            return "Draws a circle.";
        }
    }


    class Program
    {
        static void Main(string[] args)
        {
            IDrawing drawing = new CircleDrawing(); //Get a circle drawing which will be used later.
            IShape shape = new CircleShape(drawing);// Get a circle shape which uses drawing object to draw.
            Console.WriteLine(shape.Draw());//Ok, shape draws.
            Console.ReadKey();
        }
    }
}

输出：