Object Oriented Programming-Object Oriented Programming-Lecture Slides, Slides of Object Oriented Programming

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Outlines

Object Oriented Programming

Classes

Data Members and Member Functions

Access Specifier

Special Member Functions

Example of Class

Why OOP?

Summary

Object Oriented Programming

 Programmer thinks about and defines the

attributes and behavior of objects.

 Often the objects are modeled after real-

world entities.

Classes

Class has data members and functions

Data members are usually used only inside

the class and cannot be access from outside

Member functions are can also be accessed

in main

But this is not a rule ,sometimes opposite to it

may be the case

Member Access specifier

 Within the body, the keywords private: and

public: specify the access level of the

members of the class.

– the default is private.

 Usually, the data members of a class are

declared in the private: section of the class

and the member functions are in public:

section.

Classes

 Member access specifiers

– public:

 can be accessed outside the class directly.

– The public stuff is the interface.

– private:

 Accessible only to member functions of class

 Private members and methods are for internal use

only.

Object

Any physical thing that can be felt or seen

A class is a type, and an object of this class is

just a variable.

Also called Instance

Distinction is that object is only definition of a

thing whereas instance is actual manipulation

Special Member Functions

 Constructor:

– Public function member

– called when a new object is created

(instantiated).

– Initialize data members.

– Same name as class

– No return type

– Several constructors

Special Member Functions

class Circle

private:

double radius;

public:

Circle();

Circle(int r);

void setRadius(double r);

double getDiameter();

double getArea();

double getCircumference();

Constructor with no

argument

Constructor with one

argument

Implementing class Functions

2. Member functions defined inside class

– Do not need scope resolution operator, class

name;

class Circle

private:

double radius;

public:

Circle() { radius = 0.0;}

Circle(int r);

void setRadius(double r){radius = r;}

double getDiameter(){ return radius *2;}

double getArea();

double getCircumference();

Defined

inside

class

class Circle

private:

double radius;

public:

Circle() { radius = 0.0;}

Circle(int r);

void setRadius(double r){radius = r;}

double getDiameter(){ return radius *2;}

double getArea();

double getCircumference();

Circle::Circle(int r)

radius = r;

double Circle::getArea()

return radius * radius * (22.0/7);

double Circle:: getCircumference()

return 2 * radius * (22.0/7);

Defined outside class

class Circle

private:

double radius;

public:

Circle() { radius = 0.0;}

Circle(int r);

void setRadius(double r){radius = r;}

double getDiameter(){ return radius *2;}

double getArea();

double getCircumference();

Circle::Circle(int r)

radius = r;

double Circle::getArea()

return radius * radius * (22.0/7);

double Circle:: getCircumference()

return 2 * radius * (22.0/7);

void main() { Circle c1,c2(7);

cout<<“The area of c 1 :” <<c1.getArea()<<“\n”;

//c1.raduis = 5;//syntax error c1.setRadius(5);

cout<<“The circumference of c 1 :” << c1.getCircumference()<<“\n”;

cout<<“The Diameter of c 2 :” <<c2.getDiameter()<<“\n”; }

The first

constructor is

called

The second

constructor is

called

Since radius is a

private class data

member

class Circle

private:

double radius;

public:

Circle() { radius = 0.0;}

Circle(int r);

void setRadius(double r){radius = r;}

double getDiameter(){ return radius *2;}

double getArea();

double getCircumference();

Circle::Circle(int r)

radius = r;

double Circle::getArea()

return radius * radius * (22.0/7);

double Circle:: getCircumference()

return 2 * radius * (22.0/7);

void main() { Circle c(7); Circle *cp1 = &c; Circle *cp2 = new Circle(7);

cout<<“The are of cp 2 :” <<cp2->getArea();

}

Another class Example

 This class shows how to handle time parts.

class Time { private: int hour,minute,second; public: Time(); Time(int h,int m,int s); void printTime(); void setTime(int h,int m,int s); int getHour(){return hour;} int getMinute(){return minute;} int getSecond(){return second;} void setHour(int h){hour = h;} void setMinute(int m){minute = m;} void setSecond(int s){second = s;} ~Time(); };*

Destructor

**Time::Time() { hour = new int; minute = new int; second = new int; *hour = minute = second = 0 ; }

**Time::Time(int h,int m,int s) { hour = new int; minute = new int; second = new int; *hour = h; minute = m; second = s; }

**void Time::setTime(int h,int m,int s) { *hour = h; minute = m; second = s; }

Dynamic locations should be allocated to pointers first