Proxy模式

目录

1. 定义
2. UML
3. 参与者
4. 示例

定义：

代理模式给某一个对象提供一个代理对象，并由代理对象控制对原对象的引用。

UML:

参与者：

抽象主题(Subject)角色:

声明了代理主题和真实主题的公共接口,使任何需要真实主题的地方都能用代理主题代替.

具体主题(RealSubject)角色：

实现抽象主题角色的具体对象。

代理主题(Proxy)角色:

含有真实主题的引用,从而可以在任何时候操作真实主题,代理主题功过提供和真实主题相同的接口,使它可以随时代替真实主题.代理主题通过持有真实主题的引用,不但可以控制真实主题的创建或删除,可以在真实主题被调用前进行拦截,或在调用后进行某些操作.

示例：

using System; namespace DoFactory.GangOfFour.Proxy.Structural{  /// <summary>  /// MainApp startup class for Structural  /// Proxy Design Pattern.  /// </summary>  class MainApp  {    /// <summary>    /// Entry point into console application.    /// </summary>    static void Main()    {      // Create proxy and request a service      Proxy proxy = new Proxy();      proxy.Request();       // Wait for user      Console.ReadKey();    }  }   /// <summary>  /// The 'Subject' abstract class  /// </summary>  abstract class Subject  {    public abstract void Request();  }   /// <summary>  /// The 'RealSubject' class  /// </summary>  class RealSubject : Subject  {    public override void Request()    {      Console.WriteLine("Called RealSubject.Request()");    }  }   /// <summary>  /// The 'Proxy' class  /// </summary>  class Proxy : Subject  {    private RealSubject _realSubject;     public override void Request()    {      // Use 'lazy initialization'      if (_realSubject == null)      {        _realSubject = new RealSubject();      }       _realSubject.Request();    }  }}

Output

Called RealSubject.Request()

实际运用：

using System; namespace DoFactory.GangOfFour.Proxy.RealWorld{  /// <summary>  /// MainApp startup class for Real-World  /// Proxy Design Pattern.  /// </summary>  class MainApp  {    /// <summary>    /// Entry point into console application.    /// </summary>    static void Main()    {      // Create math proxy      MathProxy proxy = new MathProxy();       // Do the math      Console.WriteLine("4 + 2 = " + proxy.Add(4, 2));      Console.WriteLine("4 - 2 = " + proxy.Sub(4, 2));      Console.WriteLine("4 * 2 = " + proxy.Mul(4, 2));      Console.WriteLine("4 / 2 = " + proxy.Div(4, 2));       // Wait for user      Console.ReadKey();    }  }   /// <summary>  /// The 'Subject interface  /// </summary>  public interface IMath  {    double Add(double x, double y);    double Sub(double x, double y);    double Mul(double x, double y);    double Div(double x, double y);  }   /// <summary>  /// The 'RealSubject' class  /// </summary>  class Math : IMath  {    public double Add(double x, double y) { return x + y; }    public double Sub(double x, double y) { return x - y; }    public double Mul(double x, double y) { return x * y; }    public double Div(double x, double y) { return x / y; }  }   /// <summary>  /// The 'Proxy Object' class  /// </summary>  class MathProxy : IMath  {    private Math _math = new Math();     public double Add(double x, double y)    {      return _math.Add(x, y);    }    public double Sub(double x, double y)    {      return _math.Sub(x, y);    }    public double Mul(double x, double y)    {      return _math.Mul(x, y);    }    public double Div(double x, double y)    {      return _math.Div(x, y);    }  }}

Output

4 + 2 = 6
4 - 2 = 2
4 * 2 = 8
4 / 2 = 2