CODESAMPLE

Proxy - Swift

Proxy Swift

The Proxy pattern provides a surrogate or placeholder for another object to control access to it. This is useful for adding security, logging, or other cross-cutting concerns without modifying the original object. The proxy has the same interface as the real object, allowing clients to interact with it transparently.

Here, Subject defines the interface. RealSubject is the actual object with the resource. Proxy acts as the intermediary, controlling access to RealSubject. The Proxy checks a condition (e.g., authentication) before delegating to the RealSubject. This implementation uses Swift’s protocol-oriented programming, defining the Subject as a protocol and conforming to it with concrete types. This is a common and idiomatic approach in Swift for achieving polymorphism and defining interfaces.

// Define the Subject interface
protocol Subject {
    func request()
}

// The RealSubject class
class RealSubject: Subject {
    func request() {
        print("RealSubject: Handling request.")
    }
}

// The Proxy class
class Proxy: Subject {
    private var realSubject: RealSubject?

    init() {
        // Potentially lazy load the real subject
    }

    private func createRealSubject() {
        realSubject = RealSubject()
    }

    func request() {
        if realSubject == nil {
            createRealSubject()
        }

        // Add some logic here - e.g., check permissions, log access
        print("Proxy: Checking access before firing real request.")
        realSubject?.request()
    }
}

// Client code
let proxy = Proxy()
proxy.request()
proxy.request() // Demonstrates potential lazy loading