Module 04 Solutions

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Exercise 00: Polymorphism

Virtual functions for runtime polymorphism.

Animal.hpp

class Animal {
protected:
    std::string _type;
public:
    Animal();
    Animal(const Animal& other);
    Animal& operator=(const Animal& other);
    virtual ~Animal();  // VIRTUAL destructor!

    virtual void makeSound() const;  // VIRTUAL for polymorphism
    std::string getType() const;
};

Dog.cpp

Dog::Dog() : Animal() {
    _type = "Dog";
}

void Dog::makeSound() const {
    std::cout << "Woof!" << std::endl;
}

Test polymorphism:

const Animal* pet = new Dog();
pet->makeSound();  // "Woof!" (not "Generic animal sound")
delete pet;        // Calls ~Dog() then ~Animal()

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Exercise 01: Brain (Deep Copy)

Animals with dynamically allocated Brain.

Dog.hpp

class Dog : public Animal {
private:
    Brain* _brain;  // Must deep copy!
public:
    Dog();
    Dog(const Dog& other);
    Dog& operator=(const Dog& other);
    ~Dog();
    void makeSound() const;
};

Dog.cpp

Dog::Dog() : Animal() {
    _type = "Dog";
    _brain = new Brain();
}

Dog::Dog(const Dog& other) : Animal(other) {
    _brain = new Brain(*other._brain);  // Deep copy
}

Dog& Dog::operator=(const Dog& other) {
    if (this != &other) {
        Animal::operator=(other);
        delete _brain;                    // Free old
        _brain = new Brain(*other._brain); // Deep copy
    }
    return *this;
}

Dog::~Dog() {
    delete _brain;
}

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Exercise 02: Abstract Class

Make Animal abstract with pure virtual function.

AAnimal.hpp

class AAnimal {
protected:
    std::string _type;
public:
    // ...
    virtual void makeSound() const = 0;  // Pure virtual
};

// Now: AAnimal a; is ERROR (cannot instantiate abstract class)

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Exercise 03: Materia Interface

Interfaces and the clone pattern.

ICharacter.hpp

class ICharacter {
public:
    virtual ~ICharacter() {}
    virtual std::string const& getName() const = 0;
    virtual void equip(AMateria* m) = 0;
    virtual void unequip(int idx) = 0;
    virtual void use(int idx, ICharacter& target) = 0;
};

Ice.cpp

AMateria* Ice::clone() const {
    return new Ice(*this);  // Return new copy
}

MateriaSource.cpp

AMateria* MateriaSource::createMateria(std::string const& type) {
    for (int i = 0; i < 4; i++) {
        if (_templates[i] && _templates[i]->getType() == type)
            return _templates[i]->clone();
    }
    return NULL;
}