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

Download Object Oriented Programming-Object Oriented Programming-Lecture Slides and more Slides Object Oriented Programming in PDF only on Docsity! Outlines Object Oriented Programming Classes Data Members and Member Functions Access Specifier Special Member Functions Example of Class Why OOP? Summary docsity.com Object Oriented Programming  Programmer thinks about and defines the attributes and behavior of objects.  Often the objects are modeled after real- world entities. docsity.com 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. docsity.com Syntax class_nameclass { private: … … … public: … … … }; Public members or methods private members or methods docsity.com 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. docsity.com 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 docsity.com 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 docsity.com Implementing class Functions  Class implementation: writing the code of class methods.  There are two ways: 1. Member functions defined outside class  Using Binary scope resolution operator (::)  “Ties” member name to class name  Uniquely identify functions of particular class  Different classes can have member functions with same name – Format for defining member functions ReturnType ClassName::MemberFunctionName( ){ … } docsity.com Accessing Class Members  Operators to access class members – Identical to those for structs – Dot member selection operator (.)  Object  Reference to object – Arrow member selection operator (->)  Pointers docsity.com 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 c1:” <<c1.getArea()<<“\n”; //c1.raduis = 5;//syntax error c1.setRadius(5); cout<<“The circumference of c1:” << c1.getCircumference()<<“\n”; cout<<“The Diameter of c2:” <<c2.getDiameter()<<“\n”; } The first constructor is called The second constructor is called Since radius is a private class data member docsity.com 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 cp2:” <<cp2->getArea(); } docsity.com 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 docsity.com void Time::printTime() { cout<<"The time is : ("<<*hour<<":"<<*minute<<":"<<*second<<")" <<endl; } Time::~Time() { delete hour; delete minute;delete second; } void main() { Time *t; t= new Time(3,55,54); t->printTime(); t->setHour(7); t->setMinute(17); t->setSecond(43); t->printTime(); delete t; } Output: The time is : (3:55:54) The time is : (7:17:43) Press any key to continue Destructor: used here to de- allocate memory locations When executed, the destructor is called docsity.com Reasons for OOP 1. Simplify programming 2. Interfaces  Information hiding: – Implementation details hidden within classes themselves 3. Software reuse  Class objects included as members of other classes docsity.com