How to use virtual functions to achieve a polymorphic behavior in C++?

Question

I am new to these important features of C++, i have already read a few question/answers on these topics here and googled a few docs. But i am still confused with this...

<

Answer 1

Here's the best explanation of polymorphism that I've ever heard:

There are many animals in this world. Most of them make some sound:

class Animal
{
public:
    virtual void throwAgainstWall() { };
};

class Cat : public Animal
{
public:
    void throwAgainstWall(){ cout << "MEOW!" << endl; }
};

class Cow : public Animal
{
public:
    void throwAgainstWall(){ cout << "MOOO!" << endl; }
};

Now imagine you have huge bag with animals and you can't see them. You just grab one of them and throw it against wall. Then you listen to its sound - that tells you what kind of animal it was:

set<Animal*> bagWithAnimals;
bagWithAnimals.insert(new Cat);
bagWithAnimals.insert(new Cow);

Animal* someAnimal = *(bagWithAnimals.begin());
someAnimal->throwAgainstWall();

someAnimal = *(bagWithAnimals.rbegin());
someAnimal->throwAgainstWall();

You grab first animal, throw it against wall, you hear "MEOW!" - Yeah, that was cat. Then you grab the next one, you throw it, you hear "MOOO!" - That was cow. That's polymorphism.

You should also check Polymorphism in c++

And if you are looking for good book, here is good list of 'em: The Definitive C++ Book Guide and List