Proxy Pattern in Design Patterns

Proxy Pattern

• A design pattern providing a surrogate or placeholder for another object, controlling access.
• Aims to add intermediary layers between clients and objects, for functionality, security or performance improvements.
• Real-world examples include access control, logging, caching, and remote object access.

Proxy Pattern Structure

• A Proxy class that implements the same interface as the original object.
• A Real Subject class that represents the actual object being accessed.

Proxy Pattern Diagram

• Subject Interface: Defines common methods and properties for both RealSubject and Proxy.
• RealSubject Class: The actual object the client wants to access. Implements methods from the interface.
• Proxy Class: Implements the same interface as the original object. Controls access to the RealSubject. This can intercept requests, add functionality or delegate to RealSubject.
• Client: Interacts with the Proxy object and believes it's directly interacting with the RealSubject.

Advantages of Proxy Pattern

• Access Control: The Proxy controls access to the RealSubject based on specific criteria.
• Lazy Initialization: The Proxy can delay the creation of the RealSubject until it is needed, improving performance and reducing resource usage.

Example: Location-Based Website Access Proxy

• A scenario where a proxy restricts website access based on user location.
• A LocationBasedWebAccessProxy controls whether a website is accessible to a specific user based on their location.
• The example involves a client, Proxy, and RealSubject objects, to control website access.
• The output shows examples of how the method is working in a programming language (csharp) and demonstrates website access based on different user locations.

Step-by-Step Implementation (Example)

• Step 1: Define the Subject Interface (IWebAccess). This defines the method for accessing websites along with URL and user location as parameters.
• Step 2: Implement the Real Subject (RealWebAccess). This class implements the actual logic of accessing the websites.
• Step 3: Implement the Proxy (LocationBasedWebAccessProxy). This class checks the user's location before allowing access.
• Step 4: Client Code (example). This shows how a client could use the proxy for website access, demonstrating the access control logic.

Explore the Proxy Pattern, a crucial design pattern that acts as a surrogate or placeholder to control access to an object. This quiz covers its structure, including the relationships between the Proxy, Real Subject, and Client. Test your understanding of how this pattern can enhance functionality, security, and performance.