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Object Oriented

Programming

Instructor: M.Imran khalil

©University of Sargodha Canal Campus

Lahore

What is OOP?

• Why oop? – Limitations of procedural approch – A litle background or functions

• Oop is real word modeling • A technique for system modeling


Lahore

1

What is an Object?

An object is

• Something tangible (Ali, Car) • Something that can be apprehended

intellectually (Time, Date)


Lahore

What is an Object?

An object has

• State (attributes) • Well-defined behaviour (operations) • Unique identity

©University of Sargodha Canal Campus Lahore

2

Example – Car is a Tangible Object

• State (attributes) - Color - Model

• behaviour (operations)

- Accelerate - Start Car

- Change Gear • Identity

- Its registration number


Lahore

Class

• Class is a tool to realize objects • Class is a tool for defining a new type • Class is user defined data type


3

Object Oriented Programing

Instructor: M.Imran khalil


Review

• What is oop? • Class • Object

– Attributes/Data Members – Factions/ methods

• Syntax of defining class • Creating objects of class


1

Class

• A class has

–Data

–Function


Lahore

Today Topic

• How to access a member of class • Member Functions • Access modifier • Constructor • Destructor


2

Today Example

class Date

{

int day ; int month ; int year ;

} ;


Lahore

Example cont..

main ( )

{

Date mydate; mydate.month = 10 ; // Error

}


3


Instructor: M.Imran Khalil

Resource:Imrankhalil3.wordpress.com


A small tip

1

A little Review

• Member Functions • Access modifier

• Public • Private

• Constructor


Constructor

• A constructor is a member function that is executed automatically whenever an object is created.

• It has following special features Has Same name as class name Has no return Type Is usually public

• Why we use constructor??


2

Constructor cont.…

• Constructor is used to make object in well defined form.

Example

class Student {

int

rollNo; public: Student()

{ rollNo = 100;

} }; int main() { Student aStudent;/*constructor is explicit called at this

point*/ } };

3



Resource:Imrankhalil3.wordpress.com


A small tip

1

A little Review

• Member Functions • Access modifier

• Public • Private

• Constructor


Constructor

• A constructor is a member function that is executed automatically whenever an object is created.

• It has following special features Has Same name as class name Has no return Type Is usually public

• Why we use constructor??


2

Constructor cont.…

• Constructor is used to make object in well defined form.

Example

class Student {

int

rollNo; public: Student()

{ rollNo = 100;

} }; int main() { Student aStudent;/*constructor is explicit called at this

point*/ } };

3

Lecture 4



[email protected]

Resource: Imrankhalil3.wordpress.com


Review

•Constructor

•Default constructor

•Destructor

•Inline functions

1

mailto:[email protected]

Imrankhalil3.wordpress.com

Now Its time to self assessment !

• Create a class Rectangle with attributes length and width, each of which defaults to 1. Provide member functions that calculate the perimeter and the area of the rectangle. Also, provide set and get functions for the length and width attributes. The set functions should verify that length and width are each floating-point numbers larger than 0.0and less than 20.0.

Today’s lecture

• Todays lecture contents

• UML diagrams to represent classes • UML Symbols for classes and

their relationships • Composition • Aggregation

2

What’s UML

• The UML is a graphical “language” for modeling computer programs.

• “Modeling” means to create a simplified representation of something, as a blueprint models a house.

• The UML provides a way to visualize the higher-level organization of programs without getting mired down in the details of actual code.

• UML is simply a way to look at the software being • developed

Graphical Representation of Classes

(Class Name)

(attributes)

(operations)

(Class Name)

Suppressed

Form

Normal Form 3

Lecture 5

Object Oriented

Programing


[email protected]

Resource: Imrankhalil3.wordpress.com ©University of Sargodha Canal Campus Lahore

Review

UML diagrams to represent classes

Function overloading

Same function performing similar task


1



14/10/2013

Today’s Lecture

Constructor Overloading

Scope Resolution Operator


Constructor Overloading Constructors can have parameters

These parameters are used to initialize the data members with user supplied data

Constructors with different parameters are called overloaded constructors


2

14/10/2013

Example

class Date{

int day, month, year;

public: Date() {

day=0; month=0; year=0; } Date(int d, int m, int y) {

day=d; month=m; year=y; }

};

Void main()

{

Date mydate;

Date urdate(10,12,2013);

}


3

15/5/2013

Lecture 6

Object Oriented

Programing


[email protected]


Today’s lecture

Operators

Syntax for overloading operators

How to overload operators


1



15/5/2013

Getting Start Operator Overloading Operator overloading is one of the most exciting features of

object-oriented programming.

It can transform complex, obscure program listings obvious ones. For example

statements like

d3.addobjects(d1, d2);

or the similar but equally

obscure d3 = d1.addobjects(d2);

can be changed to the much more

readable d3 = d1 + d2; ©University of Sargodha Canal Campus Lahore

Overloading Using operator overloading we can perform basic

operations on our own defined classes objects in the similar way as we perform them on basic built-in types(like int, float, long, double)

For example we can write

Object3=Object1+object2;


2

15/5/2013

Example

Date Class


class Date

{

int day; int month; int year;

};


3

13/5/2013

Lecture 7

Object Oriented

Programing


[email protected]


Review

In Last Lecture we studied about

Syntax of Overloading

Overloading Unary Operator

Overloading postfix and postfix ++ operator


1



13/5/2013

Review of Last Lecture Types for operator overloading

Built in (int, char) or user-defined (classes)

Can use existing operators with user-defined types

Cannot create new operators

Overloading operators

Create a function for the class

Name of operator function

Keyword operator followed by symbol

Example

operator+ for the addition operator +


Restrictions on Operator Overloading Overloading restrictions

Precedence of an operator cannot be changed

Associativity of an operator cannot be changed

Arity (number of operands) cannot be changed

Unary operators remain unary, and binary operators remain binary

No new operators can be created

Use only existing operators

No overloading operators for built-in types

Cannot change how two integers are added

©University

of SargodhaProducesCanalCampusLahorea syntax error

2

13/5/2013

Today’s lecture

A little more discussion on overloading

Overloading binary operators

Overloading + operator

Overloading -+ operator


Operator Overloading

Operator Overloading enables to apply standard

operators (such as +,-,*,<, and so on) to objects of the programmer defined type.

int a = b +

c;

Function name

operator+

Returns an int int data type

Calling Party

Stored in a

L-Value

int data type

Argument to function R-

Value , Called Party

It helps to enhance simplicity in program structure.


Lecture 9

Object Oriented

Programing


[email protected]

Resource: Imrankhalil3.wordpress.com

Today’s Lecture

Static Data Member

Static Member function

2 1



Static Class Members

When a class variable is static, only one memory

location is allocated

All members of the class share a single storage location for a static data member of that same class

When you create a non-static variable within a function, a new variable is created every time you call that function

When you create a static variable, the variable maintains its memory address and previous value

for the life of the program.

3

When you Need it?

When you need it ?

A static data item is useful when all objects of the same class must share a common item of information.

static class data member is used to share information among the objects of a class.

4 2

Example class foo { private: static int count; //only one data item for all

objects //note: “declaration” only! public: foo() //increments count when object created {

count++; }

int getcount() //returns count { return count;

} }; //End of class

5 int foo::count = 0; //*definition* of count

int main() { foo f1, f2, f3; //create three objects cout << “count is “ << f1.getcount() << endl; //each

object cout << “count is “ << f2.getcount() << endl;

//sees the cout << “count is “ << f3.getcount() << endl;

//same value return 0; }

6 3

5/12/2013

Lecture 10

Object Oriented

Programing


[email protected]


Revision of Previous lecture

In previous lecture we discussed

Static Data Member

Static Member Function


1



5/12/2013

Inheritance

A child inherits characteristics of its parents

Besides inherited characteristics, a child may have its own unique characteristics


Inheritance in Classes If a class B inherits from class A then it contains

all the characteristics (information structure and behavior) of class A

The parent class is called base class and the child class is called derived class

Besides inherited characteristics, derived class may have its own unique characteristics


2

5/12/2013

Example – Inheritance

Person

Doctor

Student

Teacher ©University of Sargodha Canal Campus Lahore

Inheritance

Inheritance is the process of creating new classes, called derived classes, from existing or base classes.


3

08/12/2014

Lecture 11

Object Oriented

Programing


[email protected]


Review of Last Lecture

In Previous lecture we learned

Inheritance between classes

Parent class is called Base Class and Child Class is called Derived class

There is a relation called “Is A” Or “Is a Kind of” between Base class and child class

Generalization

Extension

Specialization


1



08/12/2014

Todays Topic

Practically implementation of Inheritance in C++


Inheritance

It is the mechanism of deriving new class from existing

class.It provides the idea of reusability.

A B

Base , super,parent class

derived , sub, child class

2

08/12/2014

Inheritance Syntax The simplest example of inheritance requires two classes: a base

class and a derived class.

The base class OR super-class does not need any special syntax.

The derived class OR subclass on the other hand, must indicate that it’s derived from the base class.

This is done by placing a colon after the name of the

derived class, followed by a keyword such as public and then the base class name.

Syntax of inheritance in c++

Keyword Child class name

Parent class name

Class Child: public parent

MODE OF

INHARITACE

3

Lecture 12

Object Oriented

Programing INSTRUCTOR: M.IMRAN KHALIL [email protected] RESOURCE: IMRANKHALIL3.WORDPRESS.COM

Todays topic

Stream Classes

File handling

16/6/2013

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1



16/6/2013

Stream Classes

A stream is a general name given to a flow of

data

In C++ a stream is represented by an object of a particular class.

So far we’ve used the cin and cout stream objects.

Why using stream classes ??

Stream class hierarchy

2

16/6/2013

Cont…

The ios class is the base class for the hierarchy.

contains many constants and member functions common to input and output operations of all kinds.

The istream and ostream classes are derived from ios and are dedicated to input and output,

The istream class contains such functions as get(), getline(), read(), and the overloaded extraction (>>) operators, while ostream contains put()and write(), and the over-loaded insertion (<<) operators.

Disk File I/O with Streams Most programs need to save data to disk files and read it back in.

Working with disk files requires another set of classes:

ifstream for input, fstream for both input and output.

ofstream for output. Objects of these classes can be associated with disk files, and we can use

their member functions to read and write to the files.

Ifstream is derived from istream.

fstream is derived from iostream, and ofstream is derived from ostream.

3

17/6/2013

Lecture 13

Object Oriented

Programing


[email protected]


Todays Lecture

Composition

Aggregation


1



17/6/2013

Composition

An object may be composed of other smaller objects

The relationship between the “part” objects and the “whole” object is known as Composition

Composition is represented by a line with a filled-diamond head towards the composer object


Example – Composition of Ali

Head

1

Arm 2

Ali 2

Leg

1

©University of Sargodha Canal Campus Lahore Body

2

17/6/2013

Example – Composition of Chair

Back

1

Chair

2 1 4

©UniversityArm of Sargodha Canal Campus Lahore Seat Leg

Composition: Objects as Members of

Classes

Composition

Composition is “consists of” relation Ship

A class can have objects of other classes as members

©University of Sargodha Canal Campus Lahore 3

15/12/2014

Lecture 15

Object Oriented

Programing


[email protected]


Today’s Lecture

Static and Dynamic Binding

Virtual and Pure Virtual Functions

Abstract Class

Multiple Inheritance

Problems with Multiple inheritance


1



15/12/2014

Dynamic Method Binding Inheritance in OOP opens up many interesting properties.

One of the main advantages of inheritance is that some derived class D has all of the members of its base class B.

Once D is not hiding any of the public members of B, then it is possible for an object of D to represent B in any context where a B could be used.

This feature is known as subtype polymorphism.

Lets illustrate an example:


An Example of Dynamic Binding

class person {

… void person :: print() { // prints details for the person }

}; class student : public person {

… void student :: print () { //adds more specific information }

}; class lecturer : public person {

… void lecturer :: print () { //adds more details }

}; …

new student (); person *x = s;

lecturer (); person *y = t; s -> print (); x -> print () ;

©University of Sargodha Canal Campus Lahore t -> print (); y -> print () ;

This is a polymorphic call

2

15/12/2014

Example cont…

person *x = s;

person *y = t; • -> print () ; • -> print () ;

Does the choice of the method to be called depend on the types of x and y ?

If so then this is known as static binding.

Does the choice of the method to be called depend on the classes of the objects s and t to which those variables refer ?

If so then is known as dynamic binding.

Dynamic binding is central to OOP and ensures that even if we are using the base class to refer to a child class, the correct methods will always be called.


Virtual Methods

C++ uses static binding by default.

Hence we must explicitly state that we wish to use dynamic binding.

To do this we can use the virtual keyword.

By changing the code in the previous example to look like

this: class person { … virtual void print () { // print person details

} }; With virtual methods, calls are dispatched to the appropriate implementation at

runtime, based upon the class of the object.


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