About coding

Hi Guys,

I wanted to know that if we have a class of student as:

Code:

class student

{

private:

int roll_no;
char name;
int age;

public:
int getroll_no();
char getname();

};
main()

{

char student :: getname()
int   student :: getroll_no()

}

-------------------------------------------------------------------
If we use the codes in bold is it possible that we can access the private data members of the class using the functions in public?

Thanks

Yes
SetName(<value>) //Set the value
GetName() //return that value, wich was previously set
those functions work to acces private data

Actually, no. Well, not the way you've tried to do it, anyways.

You're going to have to be clearer on a few things.

Firstly, you have defined student's name member as a single char. There aren't many students, regardless of nationality, who's name is a single character. Either make the name an array of char or (better) make the name of type std::string (which represents a set of characters internally). std::string is a type in the standard header named <string>.

Second, it is not possible to just declare member functions in main() and use them - compilers will object. They need to be defined somewhere else. More importantly, non-static member functions can only be used on an instance of the class. They cannot be called standalone. So

Code:

//  your definition of the student class

int student::getroll_no() {return roll_no;}    // implement the getroll_no() member function

int main()
{
    student person;
    int number = person.getroll_no();    // this will work:  person is an instance of student

    student::getroll_no();    // this will not compile as it is not operating on an instance of student

    person.student::getroll_no();      // this will also work
}

Mind you, given that your code provides no means to set the name and roll_no methods of a student (for example, a user-defined constructor) there is no point in having the member functions to get their values.

Hi,
Thanks for your reply, so in the function:
student::getroll_no();
You said that it doesnot belong to the instance of the student,what do you mean by instance?
But I have defined this function getroll_no() in the class of student.

int number = person.getroll_no(); ---> Does this function gets parameters and stores them in the "int number"?

Originally Posted by student111

so in the function:
student::getroll_no();
You said that it doesnot belong to the instance of the student

grumpy stated that "this will not compile as it is not operating on an instance of student".

Originally Posted by student111

what do you mean by instance?

An instance of the class is an object of the class.

Originally Posted by student111

But I have defined this function getroll_no() in the class of student.

Yes. However, it is a non-static member function, so it must operate on an object of the student class.

Hi,
Ok it was my mistake ,so the object should be declared before we could use the function.
Eg

Code:

main()
{
 student std1;
 std1.getname(); 

}

where "std1" is the object for the class student.

So what do these functions do :
char student :: getname()
int student :: getroll_no()

Originally Posted by student111

H
So what do these functions do :
char student :: getname()
int student :: getroll_no()

In your original code snippet, they would guarantee a compiler error. You cannot use that syntax within the body of a function.

In the code snippet I gave (if you replace the first line with your class definition) the code will compile. That syntax is used to define those member functions outside the body of the student class.

student111, I recommend you look at a tutorial about classes.
Furthermore, you should post working code so that we can understand if you are merely using a legacy compiler or just posting pseudo code (and find syntax errors).