oop concepts classes_objects

Development Software 2 (DOS200S)

2013

OBJECT ORIENTED

PROGRAMMING CONCEPTS

Compiled By WH Olivier 2013/01/29 1

Introduction Classes & Objects

2013/01/29 Compiled By WH Olivier 2

In the real world, an object can be anything that we can see

around us. An object can be of a certain type. A dog, for

instance is a type of animal.

Animals is characterized by the way they look and the way they

behave.

A dog belong to the animal class and therefore inherits the

properties and behavior of an animal.

A Dalmatian again, is a type of dog and would inherit the

properties and the behavior of a dog.

Therefore, we can differentiate between a class and an

object.

A Class is a blueprint or template for an object. A class

specifies or defines an objects properties and behavior.

An Object is an instance of a class or type. Two dogs

would possess different values for their color and size

properties.

Classes & Objects cont…


A Car Class


The creation of a car typically begins as engineering drawings. The drawings would include all the features, components and properties of the car. Included in the design would be all the mechanisms that will allow the car to perform some function.

For example, in order for a car to accelerate, pressing the pedal would perform that function.

Unfortunately you cannot drive the drawings. Building a car from that engineering drawings would be creating an instance a car. The car instance (object) would possess all the features and properties of that car class.

Once the car is there you can drive it, press the accelerator pedal and that would course the car to move faster

Read more… Introduction to classes and objects

Deitel_Objects_03_sample.pdf

Objects in Business


In the business world, companies deal with various

types of data. Data elements can be grouped

because they are related. For example all the data

about a customer are grouped and can be

represented as a Customer object.

Other objects would be Employee, Order, Invoice, etc.

Read More on Business Objects

Business Objects

Introduction to SAP Business Objects

Business_objects.pdf

Introduction_to_SAP_Business_Objects.pdf

Program design use to be (and still is being used)

procedural. Procedural programming is creating a step

by step program where the program is a sequence of

instructions . Execution of the program starts at the

top and continues executing code line by line till the

bottom.

Procedural programming also include functions

(smaller programmes) where the program can change

data which it has access to via the functions.

With procedural programming the data and the

operations on the data is separate and data is being

passed and changed via the functions.


In Object Oriented Programming, things are being viewed as entities called objects. Objects is the grouping of data and its related functionality into one unit.

OOP is a design philosophy used in different programming languages. Everything within OOP is grouped as a self sustainable object. OOP thus have a re-usable component where objects can be used in many other programs.

An Object is entity or thing that can perform a set of related activities / behavior (Eg. A CAR can drive, brake) and have particular characteristics / properties ( Eg. A Car have color, engine capacity)

A Class is simply a representation of a type of object. It is a blueprint for the describing the detail of an object.


The encapsulation is the inclusion within a program

object of all the resources need for the object to

function - basically, the methods and the data.

In OOP the encapsulation is mainly achieved by

creating classes, the classes expose public methods

and properties.

The class is kind of a container or capsule or a cell,

which encapsulate the set of methods, attribute and

properties to provide its indented functionalities to other

classes. In that sense, encapsulation also allows a

class to change its internal implementation without

hurting the overall functioning of the system. Compiled By WH Olivier 2013/01/29 8

Abstract classes, which declared with the abstract

keyword, cannot be instantiated. It can only be used

as a super-class for other classes that extend the

abstract class. Abstract class is the concept and

implementation gets completed when it is being

realized by a subclass. In addition to this a class can

inherit only from one abstract class (but a class may

implement many interfaces) and must override all its

abstract methods/ properties and may override virtual

methods/ properties.


Abstract data types can be implemented via classes and object.

When defining a new class and creating a object based on that class, you created an abstract data type.

Abstract data types are purely theoretical entities, used (among other things) to simplify the description of abstract algorithms, to classify and evaluate data structures, and to formally describe the type systems of programming languages.*

* http://en.wikipedia.org/wiki/Abstract_data_type Compiled By WH Olivier 2013/01/29 10

http://en.wikipedia.org/wiki/Type_system

Inheritance & Composition

The ability for a new class to be created from an

existing class by extending it is known as

inheritance.

When one class contains another class as one of

its members, that is known as composition

The following slide explains it by use of a diagram


dataType

-dMonth: int

-dDay: int

-dYear: int

+setDate(int, int, int) : void

+getDay() const: int

+getMonth() const: int

+getYear() const: int

+printDate() const: void

+dateType(int = 1, int = 1, int =1900)

partTimeEmployee Class

+print() const : void

+calculatePay() const: double

+setNameRateHours(string, string,

double, double) : void

+partTimeEmployee(string = “ “,

string = “ “, double = 0, double

= 0)

-payRate : double

-hoursWorked : double

personType Class

+print() const : void

+setName(string, string: void

+getFirtsName() const: string

+getLastName() const : string

+personType(string = “ “, string = “

“)

-firstname : string

-lastname : string

personalInfo Class

+setPersonalInfo(string, string, int,

int, int, int) : void

+printPersonalInfo() const : void

+personalInfoType(string = “ “,

string = “ “, int = 1, int =1,

int = 1900, int = 0)

-name : personType

-bDay : dateType

-personID: int

INHERITANCE

partTimeEmployee

“is a” type of

personType

COMPOSITION

personalInfo “has a”

dateType as one of

its members

COMPOSITION

personalInfo “has a”

personType as one

of its members

INHERITANCE and COMPOSITION


What is Polymorphism: Is a generic term which means ‘many shapes’ Is also means the ability to that one operation be performed by a wide

range of different things. Simply stated, a operation will perform differently depending on the way it is called and by which other thing it is being requested.

Method Overloading, Operator Overloading and Method Overriding is the different techniques used to achieve polymorphism

What is Method Overloading The ability to define several methods with the same name

What is Operator Overloading Operators like +, -, *, == are treated as polymorphic functions and as

such have different behaviours depending on the way it is called (arguments)

What is Method Overriding Is used in inheritance where a sub-class can override a specific

implementation of a method that is already provided by the super-class


Reference http://saimaterial.wordpress.com/2007/09/14/1what-

is-the-difference-between-object-oriented-programming-and-procedural-programming/

http://www.codeproject.com/Articles/22769/Introduction-to-Object-Oriented-Programming-Concep

http://math.hws.edu/eck/cs124/downloads/OOP2_from_Univ_KwaZulu-Natal.pdf

http://www.deitel.com/books/cpphtp5/cpphtp5_03_sample.pdf

http://publib.boulder.ibm.com/infocenter/dmndhelp/v7r5m1/index.jsp?topic=%2Fcom.ibm.wbpm.wid.data.doc%2Fbo%2Ftopics%2Fcbo.html

http://help.sap.com/saphelp_40b/helpdata/en/7e/5e11a84a1611d1894c0000e829fbbd/content.htm


http://saimaterial.wordpress.com/2007/09/14/1what-is-the-difference-between-object-oriented-programming-and-procedural-programming/







































http://publib.boulder.ibm.com/infocenter/dmndhelp/v7r5m1/index.jsp?topic=/com.ibm.wbpm.wid.data.doc/bo/topics/cbo.html





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