Modification in C++ Classes program through Association

[luckyali444]

hello everyone... i need some help... how can i sett and get the values in two classes through association. here is my little code that i wrote just to understand the concept of how to modify the one class attributes through association between two classes.

=========================================================
#include <iostream.h>

class Student
{
public:
Student(){}
Student(int v)
{
var = v;
}
~Student(){}
void setVar()
{
cout << "set the number: ";
cin >> var;
}
int getVar()
{
return var;
}
private:
int var;
};

class Teacher
{
public:
void setIDDDD(Student s)
{
s.setVar();
}
void getIDDDD(Student s)
{
cout <<s.getVar()<<endl;
}

private:
};

void main()
{
Student ob(41);
Teacher obj;

cout << "Set by object: " <<ob.getVar()<<endl;
ob.setVar();
cout << "Setter Value: " <<ob.getVar()<<endl;

obj.setIDDDD(ob);
obj.getIDDDD(ob);
}
==========================================================
In upper code, i am trying to set the new value in Student class through through teacher class. Setters and getters properly works and change the values with Student class object but when i set the values through Teacher class, it shows the old value sett by the Student Object.

[alwaysLearning0]

you have to pass by reference, you are passing by value, so setIDDDD(Student s) is creating a local Student and modifying the value of it but its not changing the original Student you passed.

change it to setIDDDD(Student &s)

Read about pass by value, reference and pointer.

[NewDev]

Yes ,change your function as :

void setIDDDD(Student &s)
{
s.setVar();
}
and it shld work...

Chk the below link for understanding the concept of association in C++:

http://www.go4expert.com/forums/showthread.php?t=17264

[luckyali444]

Thank you so much @alwaysLearning0 and @NewDev...

but wats the reason... why only reference works in this case, y not value as well... pls elaborate

thanks

[LB]

http://www.cplusplus.com/doc/tutorial/functions2/