C++ Polymorphism
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, think of a base class called Animal that has a method called animalSound(). Derived classes of Animals could be Pigs, Cats, Dogs, Birds - And they also have their own implementation of an animal sound (the pig oinks, and the cat meows, etc.):
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;
}
Try it Yourself »
Why And When To Use "Inheritance" and "Polymorphism"?
- It is useful for code reusability: reuse attributes and methods of an existing class when you create a new class.