Object Oriented Programming

Object Oriented Programming

B.Sc. Multimedia ComputingMultimedia Authoring

Agenda

Procedural Programming v OOP Software Objects Classes and Methods The Object Oriented Paradigm



Object-Oriented Programming is a way of describing

and structuring software systems that features objects

that contain functionality and data

Early program structure techniques kept program

functionality and data separate - so called

“procedural programming”


Procedural Programming

10 readln(sum)

20 sum = sum + x

30 writeln(“The answer is” ), sum)

.

60 GOSUB 200

.

200 readln(answer)

.

300 return



OOP places the data and functionality inside a software object - the data is siad to be encapsulated within the object


Software objectdata and

functionality


Software objects communicate with other software objects to carry out the overall function of a software system by sending messages to each other


Software object data and

functionality

Software object data and

functionality

Transport System

To model vehicles and drivers as an OOP software systemthink about the various objects, properties and functions of such asystem:

Vehicles - Type, Make, Model, Value, Registration Number

Drivers - Name, Age, Date of Birth, License Type


Transport System: Vehicle

Object: VehiclesProperties (attributes)

TypeMakeModelValueRegistration Number

Functions (methods)

Create an object of type VehicleSet the Make of vehicleGet the make of vehilceSet the value of the vehicle


Transport System: Driver

Object: Driver Properties (attributes)

NameDate of BirthLicense TypeValue

Functions (methods)

Create an object of type DriverSet the Name of a driverGet the name of a driverSet the type of licenseGet the type of license


Driver Object


Driver

Properties:

Name

Date of Birth

License Type

Set Name

Get Name

Set Date of Birth

Get Date of Birth

Functions (methods) to communicate with a Driver object

Vehicle Object


Vehicle

Properties:

Make

Model

Registration No.

Value

Set Make

Get Make

Set Registration No.

Get Registration No.

Functions (methods) to communicate with a Vehicle object

Class Definition for a Vehicle


public class Vehicle {

// ------ constructor------ //

public function Vehicle(){

} // end constructor

// ------ properties ------ //

var regNo:String;var make:String;var model:String;var saleValue:int;

Set Method Definition


// ------- set the registration number ------- //

public function setRegNumber(aRegNumber:String):void {

this.regNo = aRegNumber;

} // end setRegNumber

Get Method Definition


// -------- get the registration number ------ // public function getRegNumber():String {

var aRegNumber:String; aRegNumber = this.regNo; return aRegNumber;

} // end getRegNumber

Class Instantiation and Method References


var aCar:Vehicle = new Vehicle();

var reg:String;var make:String;

aCar.setRegNumber("BKD 1");aCar.setMake("Ferrari");

make = aCar.getMake();reg = aCar.getRegNumber();

ActionScript 3.0 Implementation Details


import uk.ac.uwe.multimedia.transport.Vehicle;

var aCar:Vehicle = new Vehicle();

var reg:String;var make:String;

aCar.setRegNumber("BKD 1");aCar.setMake("Ferrari");

make = aCar.getMake();reg = aCar.getRegNumber();

trace(make);trace(reg);

Object Oriented Programming Features

Classes are templates for objects, classes define properties and methods which dictate the state and behavior of the resulting software object

Data and related functions are contained within the same object space - encapsulation

Classes can be extended by creating subclasses which have similar properties and behaviors - inheritance

Inherited behaviors can be modified (overridden) to change the way an object responds to common messages- polymorphism

These three characteristics of OOP are often referred to as the “Object Oriented Paradigm”


Object Oriented Programming

Documents

Transcript of Object Oriented Programming