Inheritance and Polymorphism

This lesson covers two of the four pillars of OOP: inheritance and polymorphism. These concepts allow programmers to build hierarchies of related classes, promote code reuse, and write flexible programs that can work with objects of different types through a common interface.

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Inheritance

Inheritance is the mechanism by which one class (the subclass or child class) can acquire the attributes and methods of another class (the superclass or parent class). The subclass can then extend or modify the inherited behaviour.

Key Terminology

Term	Definition
Superclass (Parent class)	The class being inherited from.
Subclass (Child class)	The class that inherits from the superclass.
Base class	Another term for superclass, especially the top-level class in a hierarchy.
Derived class	Another term for subclass.
"Is-a" relationship	Inheritance models an "is-a" relationship: a Dog is an Animal.

Pseudocode Example

CLASS Animal
    PRIVATE name: STRING
    PRIVATE sound: STRING

    PUBLIC PROCEDURE new(n: STRING, s: STRING)
        name = n
        sound = s
    END PROCEDURE

    PUBLIC FUNCTION getName() RETURNS STRING
        RETURN name
    END FUNCTION