浅尝DesignPattern_Proxy

UML:

Proxy   (MathProxy)

• maintains a reference that lets the proxy access the real subject. Proxy may refer to a Subject if the RealSubject and Subject interfaces are the same.
• 维持一个引用让代理访问真正的Subject。代理可以引用一个Subject，如果RealSubject和Subject接口是相同的。
• provides an interface identical to Subject's so that a proxy can be substituted for for the real subject.
• 提供等同于Subject 的接口,这样代理就能替代真正的Subject 
• controls access to the real subject and may be responsible for creating and deleting it.
• 控制进入真正的Subject 而且负责创建和删除它
• other responsibilites depend on the kind of proxy:其他责任取决于代理的类型
  • remote proxies are responsible for encoding a request and its arguments and for sending the encoded request to the real subject in a different address space.
  • 远程代理是负责编码空间的要求，其参数和真正的问题在一个不同的地址编码发送请求。
  • virtual proxies may cache additional information about the real subject so that they can postpone accessing it. For example, the ImageProxy from the Motivation caches the real images's extent.
  • 虚拟代理可缓存的其他信息的真正Subject ，使他们可以推迟访问它。例如，ImageProxy的用处就是缓存实际图像的。
  • protection proxies check that the caller has the access permissions required to perform a request.
  • 保护代理检查调用方拥有访问权限的规定要求执行。

Subject   (IMath)

• defines the common interface for RealSubject and Proxy so that a Proxy can be used anywhere a RealSubject is expected.
• 定义RealSubject和代理的共同界面，使代理可以在任何地方使用RealSubject。

RealSubject   (Math)

• defines the real object that the proxy represents. 
• 定义了真正的对象，是代理代表的对象。

Sample:

IMath.cs

    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);
    }

Math.cs

    class Math:IMath
    {
        #region IMath 成员

        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;
        }

        #endregion
    }

MathProxy.cs

    class MathProxy:IMath
    {
        private Math math = new Math();
        #region IMath 成员

        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);
        }

        #endregion
    }

Program.cs

#region Proxy
            MathProxy proxy = new MathProxy();
            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));
            #endregion