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22.02.10 - Introduction to Objected Oriented Desig

Object Orientation​

  • OO systems are viewed as compositions of domain specific object abstractions, rather than data and functions
  • Objects associate data and behaviour
  • In a system they intercommunicate by sending messages to each other
    • Synchronous - method/function call
  • Asynchronous - Leave a message
  • An object is a domain concept
    - State - data
    - Behaviour - methods
    - Identity - unique identifier
    Setter - Method which allows us to set the value of the data in the object Getter - Method which allows us to get the current value of the data in the object

Decomposition​

Reduces how much you have to consider at the same time Procedural Decomposition splits the program into a number of procedures/functions Fewer interacting things make the problem simpler in mind Involves modelling the world in objects rather than functions

Identifying classes and objects

Java classes already exist for most of what we would want to do Abstraction means that we can deal with the classes on the basis of 'what they do' not 'how they do it'

Summary

Can decompose tasks into interacting objects Can add functions/methods to classes

objectRef.methodName()

These methods refer to the data for the current object