TypeScript 代理模式讲解和代码示例

/** * 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. */ interface Subject { request(): void; } /** * 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 implements Subject { public request(): void { console.log('RealSubject: Handling request.'); } } /** * The Proxy has an interface identical to the RealSubject. */ class Proxy implements Subject { private realSubject: RealSubject; /** * The Proxy maintains a reference to an object of the RealSubject class. It * can be either lazy-loaded or passed to the Proxy by the client. */ constructor(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 request(): void { if (this.checkAccess()) { this.realSubject.request(); this.logAccess(); } } private checkAccess(): boolean { // Some real checks should go here. console.log('Proxy: Checking access prior to firing a real request.'); return true; } private logAccess(): void { console.log('Proxy: Logging the time of request.'); } } /** * 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. */ function clientCode(subject: Subject) { // ... subject.request(); // ... } console.log('Client: Executing the client code with a real subject:'); const realSubject = new RealSubject(); clientCode(realSubject); console.log(''); console.log('Client: Executing the same client code with a proxy:'); const proxy = new Proxy(realSubject); clientCode(proxy); 

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.