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Definition
Provide a surrogate or placeholder for another object to control access to it.
Participants
The classes and/or objects participating in this pattern are:
- 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.
- Provides an interface identical to Subject's so that a proxy can be substituted for the real subject.
- Controls access to the real subject and may be responsible for creating and deleting it.
- Other responsibilites depend on the kind of proxy:
- 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.
- 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.
- Protection proxies check that the caller has the access permissions required to perform a request.
- Subject (IMath)
- Defines the common interface for RealSubject and Proxy so that a Proxy can be used anywhere a RealSubject is expected.
- RealSubject (Math)
- Defines the real object that the proxy represents.
Sample Code in C#
This structural code demonstrates the Proxy pattern which provides a representative object (proxy) that controls access to another similar object.
// --------------------------------------------------------------------------------------------------------------------// <copyright company="Chimomo's Company" file="Program.cs">// Respect the work.// </copyright>// <summary>// Structural Proxy Design Pattern.// </summary>// --------------------------------------------------------------------------------------------------------------------namespace CSharpLearning{ using System; /// <summary> /// Startup class for Structural Proxy Design Pattern. /// </summary> internal static class Program { #region Methods /// <summary> /// Entry point into console application. /// </summary> private static void Main() { // Create proxy and request a service var proxy = new Proxy(); proxy.Request(); } #endregion } /// <summary> /// The 'Subject' abstract class /// </summary> internal abstract class Subject { #region Public Methods and Operators /// <summary> /// The request. /// </summary> public abstract void Request(); #endregion } /// <summary> /// The 'RealSubject' class /// </summary> internal class RealSubject : Subject { #region Public Methods and Operators /// <summary> /// The request. /// </summary> public override void Request() { Console.WriteLine("Called RealSubject.Request()"); } #endregion } /// <summary> /// The 'Proxy' class /// </summary> internal class Proxy : Subject { #region Fields /// <summary> /// The real subject. /// </summary> private RealSubject realSubject; #endregion #region Public Methods and Operators /// <summary> /// The request. /// </summary> public override void Request() { // Use 'lazy initialization' if (this.realSubject == null) { this.realSubject = new RealSubject(); } this.realSubject.Request(); } #endregion }}// Output:/*Called RealSubject.Request()*/This real-world code demonstrates the Proxy pattern for a Math object represented by a MathProxy object.
// --------------------------------------------------------------------------------------------------------------------// <copyright company="Chimomo's Company" file="Program.cs">// Respect the work.// </copyright>// <summary>// Real-World Proxy Design Pattern.// </summary>// --------------------------------------------------------------------------------------------------------------------namespace CSharpLearning{ using System; /// <summary> /// Startup class for Real-World Proxy Design Pattern. /// </summary> internal static class Program { #region Methods /// <summary> /// Entry point into console application. /// </summary> private static void Main() { // Create math proxy var 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)); } #endregion } /// <summary> /// The 'Subject' interface /// </summary> public interface IMath { #region Public Methods and Operators /// <summary> /// The add. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> double Add(double x, double y); /// <summary> /// The div. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> double Div(double x, double y); /// <summary> /// The multiply. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> double Mul(double x, double y); /// <summary> /// The sub. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> double Sub(double x, double y); #endregion } /// <summary> /// The 'RealSubject' class /// </summary> internal class Math : IMath { #region Public Methods and Operators /// <summary> /// The add. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Add(double x, double y) { return x + y; } /// <summary> /// The div. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Div(double x, double y) { return x / y; } /// <summary> /// The multiply. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Mul(double x, double y) { return x * y; } /// <summary> /// The sub. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Sub(double x, double y) { return x - y; } #endregion } /// <summary> /// The 'Proxy Object' class /// </summary> internal class MathProxy : IMath { #region Fields /// <summary> /// The math. /// </summary> private Math math = new Math(); #endregion #region Public Methods and Operators /// <summary> /// The add. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Add(double x, double y) { return this.math.Add(x, y); } /// <summary> /// The div. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Div(double x, double y) { return this.math.Div(x, y); } /// <summary> /// The multiply. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Mul(double x, double y) { return this.math.Mul(x, y); } /// <summary> /// The sub. /// </summary> /// <param name="x"> /// The x. /// </param> /// <param name="y"> /// The y. /// </param> /// <returns> /// The <see cref="double"/>. /// </returns> public double Sub(double x, double y) { return this.math.Sub(x, y); } #endregion }}// Output:/*4 + 2 = 64 - 2 = 24 * 2 = 84 / 2 = 2*/给我老师的人工智能教程打call！http://blog.csdn.net/jiangjunshow
