Swift 3 ObjectOriented Programming - Second Edition

Working with typecasting and polymorphism

We can use the same method to cause different things to happen according to the class on which we invoke the method. In object-oriented programming, this feature is known as polymorphism.

For example, consider that we defined a talk method in the Animal class. The different subclasses of Animal must override this method to provide their own implementation of talk.

The Dog class overrode this method to print the representation of a dog barking, that is, a Woof message. On the other hand, a Cat class will override this method to print the representation of a cat meowing, that is, a Meow message.

Now, let's think about a CartoonDog class that represents a dog that can really talk as part of a cartoon. The