13-Class and Object.pdf

OBJECT ORIENTED

PROGRAMMING

Content



Classes, Objects, Member Functions and Data

Members



Defining a Class with Members



Initializing Objects with Constructors



Class Scope and Accessing Class Members

Objectives



By the end you should recognize:

 What classes, objects, member functions and data members are

 How to define a class and use it to create an object

 How to define member functions in a class to implement the class's behaviors

 How to declare data members in a class to implement the class's attributes

 How to call a member function of an object to make that member function perform its

task

 The differences between data members of a class and local variables of a function

 How to use a constructor to ensure that an object's data is initialized when the object is

created

 Class scope and accessing class members via the name of an object

4

#include<iostream> #include<string> using namespace std;

int makeAppointmnet();

int deleteAppointment();

void addPatient();

void deletePatient;

void addStaff();

double salary();

int main() {

string staffName; int staffID;

string staffPhoneNumber; string patientName;

string patientID;

string patientPhoneNumber; string appointmentDate; return 0; }

• Suppose

we

were

writing

hospital software

• This a bad representation of a

hospital

• We need to separate bits of

information.

• Need a way of referring to

the whole collection with a

5

class appointment {

public:

int makeAppointmnet();

int deleteAppointment();

};

Patient Class

// C++ code to define a staff class

class staff{ private:

// Data Members

string staffName; int staffID;

string staffPhoneNumber; public:

// Member Fucntions

7 #include <iostream>

#include <string> using namespace std;

class staff{ private:

// Data Members

string staffName; int staffID;

string staffPhoneNumber; public:

// Member Fucntions

int addStaff(); double salary(); }; int main() { staff s1; s1.staffName="customer1"; s1.staffID =4034;

cout << s1.salary();

return 0; }

This program will produce 2 compilation errors:

#1: ‘staff:: staffName ' #2: ‘staff:: staffID ' :

Access Specifiers



Access Specifiers



public

: members of a class accessible outside that class



private:

members of a class not accessible outside that class

Using Access Specifiers

#include <iostream> #include <string> using namespace std; class staff{

public:

// Data Members

string staffName; int staffID;

string staffPhoneNumber;

// Member Fucntions

int addStaff(); double salary(); }; int main() { staff s1; s1.staffName="customer1"; s1.staffID =4034;

cout << s1.salary(); return 0;

}

Using Access Specifiers (cont.)

#include <iostream> #include <string> using namespace std; class staff{

private:

// Data Members

string staffName; int staffID;

string staffPhoneNumber; public:

// Member Fucntions

int addStaff(); double salary(); }; int main() { staff s1; s1.staffName="customer1"; s1.staffID =4034;

cout << s1.salary();

return 0; }

Anything following this can be used by anyone outside the class

Variables



Local variables



Variables declared in a function definition’s body



Cannot be used outside of that function body



When a function terminates



The values of its local variables are lost



Data Members



Variables in a class definition



Exist throughout the life of the object



Each object of class maintains its own copy of attributes

Set and Get Functions



public

member functions that allow users of an object to set or

get the values of private data members



Allows the creator of the class to control how clients access

private

data

Using Set and Get Functions

#include <iostream> #include <string> using namespace std;

class staff{ private:

// Data Members

string staffName; int staffID;

string staffPhoneNumber; public:

// Member Fucntions

int addStaff(); double salary(); };

How would you adjust the class definition to include set and get functions??

How many do you need ??

Should they be private/public ??

Implementing Set & Get Functions



For each data member



Set function that sets its value



Get function that returns its value



Staff Data Members

14

string staffName;

 void setStaffName(string);

Get Functions

string getStaffName() { return staffName; }

int getStaffID() {

return staffID; }

16 #include <iostream>

#include <string> using namespace std; class staff{

private:

// Data Members

string staffName; int staffID;

string staffPhoneNumber; public:

// Member Fucntions

int addStaff(); double salary();

string getStaffName() { return staffName; }

int getStaffID() { return staffID; }

string getStaffPhoneNumber() { return staffPhoneNumber; }

};

int main(){

staff s1;

cout<< s1.getStaffName(); return 0;

Set Functions -1

void setStaffName(string s) {

staffName=s; }

void setStaffID(int id) {

staffID=id; }

void setStaffPhoneNumber(string pn) {

18 #include <string>

using namespace std; class staff{

private:

// Data Members

string staffName; int staffID;

string staffPhoneNumber; public:

// Member Fucntions

int addStaff(); double salary();

string getStaffName() { return staffName; }

int getStaffID() { return staffID; }

string getStaffPhoneNumber() { return staffPhoneNumber; }

void setStaffName(string s) { staffName=s; }

void setStaffID(int id) { staffID=id; }

void setStaffPhoneNumber(string pn) { staffPhoneNumber = pn; }

};

int main(){

staff s1;

s1.setStaffName(“Maha Q”); cout << s1.getStaffName(); return 0;

Constructors



Functions used to initialize an object’s data when it is created

Call made implicitly when object is created



Must be defined with the same name as the class



Cannot return values



Not even void

Using Constructors -1

string getStaffName() { return staffName; }

int getStaffID() { return staffID; }

string getStaffPhoneNumber() { return staffPhoneNumber; }

void setStaffName(string s) { staffName=s; }

void setStaffID(int id) { staffID=id; }

void setStaffPhoneNumber(string pn) { staffPhoneNumber = pn; } staff() {

staffName = “raha”; staffID = 123;

staffPhoneNumber = “4343434”

Exercise - 1

- Write a WebPage class which includes



The following integer data members

- Number of hits on the page

- Number of messages posted on the page

- Number of downloads from the page



The following member functions

- Default constructor initializes all data members to zero

- An increment function for each data members to increase them by 1

- Activity() function that return total activity of webpage: hits + messages + downloads

- Write a main function that declare and initialize imamUnivPage object.

- Write the statements that increase number of hits by 2, messages by 3, and

downloads by 1.

Included Sections