Inheritance

In this material you have learned about:

Objects which are used to hold data and behaviour about specific entities in our system or model.
Classes which are used to represent categories of objects with identical data and behaviour.

Handling Similarities Between Classes

In object-orientation we may form hierarchies of categories (classes), by letting classes inherit the operations, methods and attributes from a "base class" or "super class".

Inheritance defines the "is-a" or "is-a-kind-of" hierarchy between classes.

Aircraft, Cars and Bicycles are all Vehicles, and share some common properties of a Vehicle, namely the attributes speed and weight and the operations move and stop. The class Vehicle is a generalization of the classes Aircraft, Car and Bicycle. Aircraft, Car and Bicycle are specializations of the class Vehicle.

In the terminology of object-oriented programming: Vehicle is the Base class or Superclass, while car is a Subclass or Derived class.

How to Use Inheritance

Inheritance may be used for:

Sharing operations and attributes between classes to avoid unneccesary duplication of code.
Modelling specialization and generalization in the real world.
Writing general software components as "superclasses", which may be extended and tailored to specific needs in "subclasses".

Here is an example of inheritance in the C++ language.

Here is an example of inheritance in Modelling Diagrams.