Object Orientated Programming

Object Orientated Programming

1. Inheritance

   • The idea of something being passed down through some form of relationship.
   • Allows the re-use of code and to extend data and methods without affecting the original code.
     • A class can inherit attributes and methods from another class, thus becoming a derived class of the super class ( base class ).

2. Class

   • Is a definition of an object; It embodies all of the information needed to create and manipulate objects of a particular type.
     • A Template/ Blueprint that describes the properties/attributes and the methods appropriate to some real-world entity.
   • A Class has two main Sections: Description ( Attributes ) Actions ( Methods). Methods are fundamental to OO Languages. A method is a piece of code that implements onne of the behaviours of a class.

3. Polymorphism

   • The ability for an object of one class type to appear to be used by another.
     • When you instantiate an object, it has a specific data type, which is based on the class from which it was originally created.

4. Encapsulation

   • It is the hiding of the implementation of a class and controlling access to its methods and attributes.
     • The concept that data can only be accessed via the methods provided by the class.
       • Ensures Data Integrity
   • Classes can hide how they work from developers who may wish to use them in their programs.
   • Anyone using the class needs to understand the interface of the class, i.e its methods and attributes.
     • Prevents the user from tampering with objects or methods and allows changes to be made without affecting the program.

5. Objects

   • An instance of a class based on a real-world entity.
   • In order to identify an individual item, it must be described, and in OO this means creating an object.
     • The process of creating an object is known as instantiation.
       • Once instantiation has occurred, a reference to the object will be created, pointing to the location of that object in memory.

6. Description = Attributes Actions = Methods

7. Definitions

   • A template that describes the properties and methods of a real life entity = Class
   • An instance of a class of a real life entity = Object.
   • Concept that a sub class can derive its properties and methods from its Base/Super Class = Inheritance.
   • Data Hiding, Where the properties of an object can only be accessed through its methods = Encapsulation.
   • The ability of sub classes to be able to express the same characteristic differently. More specifically, it is the ability to redefine methods for derived classes. = Ploymorphism