代理模式(Proxy)

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using System;namespace RefactoringGuru.DesignPatterns.Proxy.Conceptual{ // The Subject interface declares common operations for both RealSubject and // the Proxy. As long as the client works with RealSubject using this // interface, you'll be able to pass it a proxy instead of a real subject. public interface ISubject { void Request(); } // The RealSubject contains some core business logic. Usually, RealSubjects // are capable of doing some useful work which may also be very slow or // sensitive - e.g. correcting input data. A Proxy can solve these issues // without any changes to the RealSubject's code. class RealSubject : ISubject { public void Request() { Console.WriteLine("RealSubject: Handling Request."); } } // The Proxy has an interface identical to the RealSubject. class Proxy : ISubject { private RealSubject _realSubject; public Proxy(RealSubject realSubject) { this._realSubject = realSubject; } // The most common applications of the Proxy pattern are lazy loading, // caching, controlling the access, logging, etc. A Proxy can perform // one of these things and then, depending on the result, pass the // execution to the same method in a linked RealSubject object. public void Request() { if (this.CheckAccess()) { this._realSubject.Request(); this.LogAccess(); } } public bool CheckAccess() { // Some real checks should go here. Console.WriteLine("Proxy: Checking access prior to firing a real request."); return true; } public void LogAccess() { Console.WriteLine("Proxy: Logging the time of request."); } } public class Client { // The client code is supposed to work with all objects (both subjects // and proxies) via the Subject interface in order to support both real // subjects and proxies. In real life, however, clients mostly work with // their real subjects directly. In this case, to implement the pattern // more easily, you can extend your proxy from the real subject's class. public void ClientCode(ISubject subject) { // ... subject.Request(); // ... } } class Program { static void Main(string[] args) { Client client = new Client(); Console.WriteLine("Client: Executing the client code with a real subject:"); RealSubject realSubject = new RealSubject(); client.ClientCode(realSubject); Console.WriteLine(); Console.WriteLine("Client: Executing the same client code with a proxy:"); Proxy proxy = new Proxy(realSubject); client.ClientCode(proxy); } }}

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Client: Executing the client code with a real subject:RealSubject: Handling Request.Client: Executing the same client code with a proxy:Proxy: Checking access prior to firing a real request.RealSubject: Handling Request.Proxy: Logging the time of request.