Defining a class with a member function


class is a predefined variable which is used to create a class in object oriented language.


 // Define class GradeBook with a member function displayMessage,
 // create a GradeBook object, and call its displayMessage function.
 #include <iostream>
 using namespace std;

// GradeBook class definition
class GradeBook
{
public:
// function that displays a welcome message to the GradeBook user
void displayMessage()
{
cout << "Welcome to the Grade Book!" << endl;
} // end function displayMessage
}; // end class GradeBook
// function main begins program execution
 int main()
{
GradeBook myGradeBook; // create a GradeBook object named myGradeBook
myGradeBook.displayMessage(); // call object's displayMessage function
} // end main
Output:
Welcome to the Grade Book!


Example 2:

// GradeBook class definition in a separate file from main.
3 #include <iostream>
4 #include <string> // class GradeBook uses C++ standard string class
5 using namespace std;
67
// GradeBook class definition
8 class GradeBook
9 {
10 public:
11 // constructor initializes courseName with string supplied as argument
12 GradeBook( string name )
13 {
14 setCourseName( name ); // call set function to initialize courseName
15 } // end GradeBook constructor
16
17 // function to set the course name
18 void setCourseName( string name )
19 {
20 courseName = name; // store the course name in the object
21 } // end function setCourseName
22
23 // function to get the course name
24 string getCourseName()
25 {
26 return courseName; // return object's courseName
27 } // end function getCourseName
28
29 // display a welcome message to the GradeBook user
30 void displayMessage()
31 {
32 // call getCourseName to get the courseName
33 cout << "Welcome to the grade book for\n" << getCourseName()
34 << "!" << endl;
35 } // end function displayMessage
36 private:
37 string courseName; // course name for this GradeBook
38 }; // end class GradeBook
Including class GradeBook from file GradeBook.h for use in main.
3 #include <iostream>
4  #include "GradeBook.h" // include definition of class GradeBook
using namespace std;
// function main begins program execution
8 int main()
9 {
10 // create two GradeBook objects
11 GradeBook gradeBook1( "CS101 Introduction to C++ Programming" );
12 GradeBook gradeBook2( "CS102 Data Structures in C++" );
13
14 // display initial value of courseName for each GradeBook
15 cout << "gradeBook1 created for course: " << gradeBook1.getCourseName()
16 << "\ngradeBook2 created for course: " << gradeBook2.getCourseName()
17 << endl;
18 } // end main