class explanation

[lenc222]

Hello,
I am reading a book "C++ How to Program(8th edition)",downloaded it from The Pirate Bay.
Atm I on third chapter "Introduction to Classes,Objects and Strings".
Can u plz help me in understanding C++ classes been stucked on it for 5 days already.

Here is a code sample from book:

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

//creates a GradeBook class
class GradeBook 
{
      public:
             //function that sets the course name
             void setCourseName( string name )
             {
                  courseName = name; //assigns name to data member course name (object)
             } // end function setCourseName
             
             //function that gets the course name
             string getCourseName()
             {
                    return courseName; //return the object's course name
             } //end function get course name
             
             //function that displays a welcome message
             void displayMessage()
             {
                  //this statement calls getCourseName to get the
                  //name of the course this GradeBook represents
                  cout << "Welcome to the grade book for\n" << getCourseName() << "!" << endl;
             } //end function displayMessage
             
      private:
              string courseName; //course name for this GradeBook
}; //end class GradeBook

//function main begins program execution
int main()
{
    string nameOfCourse; //string of characthers to store the course name
    GradeBook myGradeBook; //create a GradeBook object named myGradeBook
    
    //display initial value of courseName
    cout << "\nPlease  enter the course name: " << endl;
    getline( cin, nameOfCourse); //read a course name with blanks
    myGradeBook.setCourseName( nameOfCourse); // set the course name
    
    cout << endl; //outputs a blank line
    myGradeBook.displayMessage(); //display message with new course name
    
    cout << endl;
    system("PAUSE");
} //ends main 

In the setCourseName function what is the
courseName = name;
supposed to do.

In the getCourseName function
return courseName;
what value is it returning
.
.
.

Anyway I do not understand this code at all,its so confusing.
It would be nice if u could explain it. :D


Sry if english is bad,not my main language.

[Stewbond]

Your english is fine.

The class has one member: it's a std::string called courseName; You see it's defined on line 30.

This member is private, so only functions inside of the class can use it. If you are outside of the class, you need another function to get or set it. These are called "getters" and "setters" as described below.

In setCourseName, you add a string as an argument. That argument becomes the string "name". Your private member courseName is then set to name. THis is commonly called a setter because it serves no other purpose than to set the private member.

In getCourseName, you can get the value of the courseName private member. This kind of function is commonly galled a getter because it serves no other purpose than to output the private member.

A class with only a member (like courseName), a setter (like setCourseName) and a getter (like getCourseName) is rather useless. You could have just used a std::string instead. However, as soon as you start having other functions involved that do things with the private member, it becomes very useful as you want to limit access to this private member only to member functions.

[lenc222]

thanx a lot m8 :D