Polymorphism
Polymorphism means "many forms", and it occurs when we have many classes that are related to each other by inheritance.
Like we specified in the previous chapter; Inheritance lets us inherit attributes and methods from another class. Polymorphism uses those methods to perform different tasks. This allows us to perform a single action in different ways.
For example, imagine a base class Animal with a method called makeSound() . Derived classes of Animals could be Pigs, Cats, Dogs, Birds, etc. Every animal can "make a sound", but each one sounds different:
- Pig: wee wee
- Dog: bow wow
- Bird: tweet tweet
This is polymorphism - the same action (making a sound) behaves differently for each animal:
Example
// Base class class Animal { public: void animalSound() { cout << "The animal makes a sound \n";
}
};
// Derived class
class Pig : public Animal {
public: void
animalSound() {
cout << "The pig says: wee wee \n";
}
};
// Derived class class Dog : public Animal { public: void animalSound() { cout << "The dog says: bow wow \n";
}
};Remember from the Inheritance chapter that we use the : symbol to inherit from a class.
Now we can create Pig and Dog objects and override the animalSound() method:
Example
// Base class class Animal { public: void animalSound() { cout << "The animal makes a sound \n";
}
};
// Derived class class Pig : public Animal { public: void animalSound() { cout << "The pig says: wee wee \n";
}
};
// Derived class class Dog : public Animal { public: void animalSound() { cout << "The dog says: bow wow \n";
}
};
int main() {
Animal
myAnimal;
Pig myPig;
Dog myDog;
myAnimal.animalSound();
myPig.animalSound();
myDog.animalSound();
return 0;
}- It is useful for code reusability: reuse attributes and methods of an existing class when you create a new class.