flyweight design pattern.cpp

#include <iostream>
#include <unordered_map>
#include <string>
using namespace std;

// Flyweight Interface
class Flyweight {
public:
    virtual void operation(const string& extrinsicState) const = 0;
    virtual ~Flyweight() = default;
};

// Concrete Flyweight
class ConcreteFlyweight : public Flyweight {
private:
    string intrinsicState;

public:
    ConcreteFlyweight(const string& state) : intrinsicState(state) {}

    void operation(const string& extrinsicState) const override {
        cout << "ConcreteFlyweight: Intrinsic State = " << intrinsicState
             << ", Extrinsic State = " << extrinsicState << endl;
    }
};

// Flyweight Factory
class FlyweightFactory {
private:
    unordered_map<string, Flyweight*> flyweights;

public:
    ~FlyweightFactory() {
        for (auto pair : flyweights) {
            delete pair.second;
        }
    }

    Flyweight* getFlyweight(const string& key) {
        if (flyweights.find(key) == flyweights.end()) {
            flyweights[key] = new ConcreteFlyweight(key);
            cout << "Creating new flyweight for key: " << key << endl;
        } else {
            cout << "Reusing existing flyweight for key: " << key << endl;
        }
        return flyweights[key];
    }
};

// Client code
int main() {
    FlyweightFactory factory;

    Flyweight* flyweight1 = factory.getFlyweight("State1");
    flyweight1->operation("Extrinsic1");

    Flyweight* flyweight2 = factory.getFlyweight("State2");
    flyweight2->operation("Extrinsic2");

    Flyweight* flyweight3 = factory.getFlyweight("State1");
    flyweight3->operation("Extrinsic3");

    return 0;
}