学步园

使用场景：

动态的给一个对象增加一些额外的功能。主体类在多个方向的功能拓展。

实现代码：

// Decorator pattern -- Structural example </p> <p>using System;</p> <p>namespace DoFactory.GangOfFour.Decorator.Structural</p> <p>{</p> <p> /// <summary></p> <p> /// MainApp startup class for Structural </p> <p> /// Decorator Design Pattern.</p> <p> /// </summary></p> <p> class MainApp</p> <p> {</p> <p> /// <summary></p> <p> /// Entry point into console application.</p> <p> /// </summary></p> <p> static void Main()</p> <p> {</p> <p> // Create ConcreteComponent and two Decorators</p> <p> ConcreteComponent c = new ConcreteComponent();</p> <p> ConcreteDecoratorA d1 = new ConcreteDecoratorA();</p> <p> ConcreteDecoratorB d2 = new ConcreteDecoratorB();</p> <p> // Link decorators</p> <p> d1.SetComponent(c);</p> <p> d2.SetComponent(d1);</p> <p> d2.Operation();</p> <p> // Wait for user</p> <p> Console.ReadKey();</p> <p> }</p> <p> }</p> <p> /// <summary></p> <p> /// The 'Component' abstract class</p> <p> /// </summary></p> <p> abstract class Component</p> <p> {</p> <p> public abstract void Operation();</p> <p> }</p> <p> /// <summary></p> <p> /// The 'ConcreteComponent' class</p> <p> /// </summary></p> <p> class ConcreteComponent : Component</p> <p> {</p> <p> public override void Operation()</p> <p> {</p> <p> Console.WriteLine("ConcreteComponent.Operation()");</p> <p> }</p> <p> }</p> <p> /// <summary></p> <p> /// The 'Decorator' abstract class</p> <p> /// </summary></p> <p> abstract class Decorator : Component</p> <p> {</p> <p> protected Component component;</p> <p> public void SetComponent(Component component)</p> <p> {</p> <p> this.component = component;</p> <p> }</p> <p> public override void Operation()</p> <p> {</p> <p> if (component != null)</p> <p> {</p> <p> component.Operation();</p> <p> }</p> <p> }</p> <p> }</p> <p> /// <summary></p> <p> /// The 'ConcreteDecoratorA' class</p> <p> /// </summary></p> <p> class ConcreteDecoratorA : Decorator</p> <p> {</p> <p> public override void Operation()</p> <p> {</p> <p> base.Operation();</p> <p> Console.WriteLine("ConcreteDecoratorA.Operation()");</p> <p> }</p> <p> }</p> <p> /// <summary></p> <p> /// The 'ConcreteDecoratorB' class</p> <p> /// </summary></p> <p> class ConcreteDecoratorB : Decorator</p> <p> {</p> <p> public override void Operation()</p> <p> {</p> <p> base.Operation();</p> <p> AddedBehavior();</p> <p> Console.WriteLine("ConcreteDecoratorB.Operation()");</p> <p> }</p> <p> void AddedBehavior()</p> <p> {</p> <p> }</p> <p> }</p> <p>}</p> <p>