Ch 68 - Object-oriented design principles

Inheritance

The process of creating a new class based on an existing class (superclass)

Superclass

The class that is being inherited from

Subclass

The class that is inheriting from the superclass

Polymorphism

A concept in programming that allows an object to take on different forms or behaviours

Overriding

A method of polymorphism where the same identifier in the superclass is redefined in the subclass

Association

The relationship between two classes

Aggregation

An association where one class contains or references another, but can still exist independently from the the other class

Composition

A strong association where one class contains another contained class that is fully dependent on the container. If the container is destroyed, the contained object is also destroyed.

Abstract method

A method declared in an abstract class that does not have an implementation. Instead, it is used as a placeholder and must be overridden by subclass methods.

Virtual method

A method declared with an implementation in a regular class that can be optionally overridden or inherited from by other subclasses

Static method

A method that is relevant to all the instances of a class, rather than to any specific instance, and can be run without creating an object. (It essentially groups a bunch of methods under one class name for clarity, used in a lot of python libraries, e.g pygame.display.update())

Interface

A collection of abstract methods that a class must implement

OOP design principles

• Encapsulate what varies

• Favour composition over inheritance

• Program to interfaces, not implementation

Why is the OOP paradigm used?

• Modularity - Breaks down code into classes and objects with clear responsibilities

• Reusability - Through inheritance, existing code can be used without rewriting

• Maintainability - OOP is easier to understand and update

• Encapsulation - Internal object data is hidden from the outside interface