/*Decorator Pattern example*/ #include #include using namespace std; /* ----- Base ----- */ class Icecream { public: virtual float getPrice() = 0; virtual void printOrder() = 0; }; /* ---- end base ---- */ /* --- concrete bases --- */ class Cone : public Icecream { public: virtual void printOrder() { cout << "Cone (1 scoop):" << endl; } virtual float getPrice() { return 0.80; } }; class Cup : public Icecream { public: virtual void printOrder() { cout << "Cup (2 scoops):" << endl; } virtual float getPrice() { return 1.60; } }; class Bowl : public Icecream { public: virtual void printOrder() { cout << "Bowl (3 scoops):" << endl; } virtual float getPrice() { return 2.40; } }; /* --- end concrete bases --- */ /* --- Decorator 'flavour' --- */ class Flavour : public Icecream { private: Icecream* icecream; public: Flavour(Icecream* ice) : icecream(ice){} virtual void printOrder() { icecream->printOrder(); } virtual float getPrice() { return icecream->getPrice(); } }; /* --- end decorator 'flavour' --- */ /* --- Concrete flavour --- */ class Chocolate : public Flavour { public: Chocolate(Icecream* ice) :Flavour(ice){} float getPrice() { return Flavour::getPrice() + 0.00; } virtual void printOrder() { Flavour::printOrder(); cout << "Chocolate" << endl; } }; class Vanilla : public Flavour { public: Vanilla(Icecream* ice) :Flavour(ice) {} float getPrice() { return Flavour::getPrice() + 0.00; } virtual void printOrder() { Flavour::printOrder(); cout << "Vanilla" << endl; } }; /* --- end concrete flavour --- */ /* --- Decorator 'topping' --- */ class Topping : public Icecream { private: Icecream * icecream; public: Topping(Icecream* ice) : icecream(ice) {} virtual void printOrder() { icecream->printOrder(); } virtual float getPrice() { return icecream->getPrice(); } }; /* --- end decorator 'topping' --- */ /* --- Concrete topping --- */ class ChocolateSauce : public Topping { public: ChocolateSauce(Icecream* ice) : Topping(ice) {} float getPrice() { return Topping::getPrice() + 0.50; } virtual void printOrder() { Topping::printOrder(); cout << "Chocolate sauce" << endl; } }; /* --- end concrete topping --- */ /* ----- client ----- */ int main() { Icecream* john = new ChocolateSauce( new Vanilla( new Cone())); Icecream* mary = new Vanilla( new Vanilla( new Chocolate( new Bowl))); cout << setprecision(2) << fixed; cout << "John's order:" << endl; john->printOrder(); cout << "Price: " << john->getPrice(); cout << "\n\n"; cout << "Mary's order:" << endl; mary->printOrder(); cout << "Price: " << mary->getPrice(); //edit to showcase the modification at runtime: // S: Hey Tim. What do you want? // T: I'd like a cone. Icecream* tim = new Cone(); // S: Ok. what do you want in your cone? // T: A scoop vanilla, please. tim = new Vanilla(tim); // S: here we go. Order finished cout << "\n\n"; cout << "Tim's order:" << endl; tim->printOrder(); cout << "Price: " << tim->getPrice(); cout << "\n\n"; // T: actually... can I get some chocolate sauce on top of my vanilla cone? // S: Sure. tim = new ChocolateSauce(tim); cout << "Tim's order:" << endl; tim->printOrder(); cout << "Price: " << tim->getPrice(); }

Decorator pattern implementation