proxy design pattern.cpp

#include <iostream>
using namespace std;

// Subject Interface
class Subject {
public:
    virtual void request() const = 0;
    virtual ~Subject() = default;
};

// Real Subject
class RealSubject : public Subject {
public:
    void request() const override {
        cout << "RealSubject: Handling request." << endl;
    }
};

// Proxy
class Proxy : public Subject {
private:
    RealSubject* realSubject;

public:
    Proxy() : realSubject(nullptr) {}

    ~Proxy() {
        delete realSubject;
    }

    void request() const override {
        if (realSubject == nullptr) {
            realSubject = new RealSubject();
        }
        cout << "Proxy: Delegating request to RealSubject." << endl;
        realSubject->request();
    }
};

// Client code
int main() {
    Proxy proxy;
    proxy.request();
    proxy.request(); // The second request will use the already created RealSubject

    return 0;
}