When is Orientated Programming NOT?

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When is Orientated Programming NOT?

• Mike Fitzpatrick

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Types of OOP

• OOP focuses on programming with objects
• Sending data and commands to objects
• Reading data and receiving messages from objects
• Two Main Types
• Object/event based programming
• Usually focuses on visible objects
• Uses pre-defined objects
• Object orientated programming based plus
• Objects are designed and built
• Program design focuses on creation of objects

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What is an OBJECT?

• Object are actual entities
• Visible Objects on the screen
• Invisible Objects, code and data only, used to
  store and process data
• Objects receive commands, and receive and send
  data
• Objects are Instances of pre-defined classes
• They can be selected from a list of components
• Classes are definitions that
• Specify representation and behavior
• Contain data and methods to process the data

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What is an OBJECT? (cont.)

• Objects have properties/attributes descriptive
  data and event handlers
• Attributes of objects can be read and changed
• when the instance of the object is created, or
• using code in a program
• Event handlers activate procedures/functions that
  are internal to the object

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INSIDE Objects (1)

• Objects use Information Hiding
• The EXTERNAL behaviour of the object is separated
  from the INTERNAL implementation Data
  Abstraction
• The programmer only needs to see the external
  behaviour of the object when using the object

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INSIDE Objects (2)

• Encapsulated Data
• A black box has PRIVATE (Internal/Local)
• Attributes - data/variables
• Methods procedures/functions
• Communication with an object is with PUBLIC
  Properties
• Attributes
• Methods
• ALL fields and methods are attached to an object
• NO Independent Global Variables
• NO Independent Procedures/Functions

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INSIDE Objects (3)

• Class Inheritance
• A new class of objects is usually based on
  another class
• Can add, change and delete methods/attributes
• Provides genuine and easy reusability of
  programming components
• Can be added to library of components for later
  use or full libraries purchased no need to
  re-enter code and debug

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INSIDE Objects (4)

• Polymorphism
• The inherited public attribute or method of a new
  class of object can changed so that
• Is called the same BUT
• Activates a different method

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INSIDE Objects (5)
Graphical Design of an Object
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First OOP Steps - Analysis

• Identify objects, or classes, in the problem
  description (NOUNS)
• Identify processes or methods associated with
  each object (VERBS)
• Specify the attributes of each object
  (ADJECTIVES)
• Separate into Public and Private