error C2248 cannot access private member declared in class

Question

We got an exercise in c++. The teacher gave us the functions in the public part of the "class Assignment"(so I cannot change the public declaration of the functions in the header.h). I got an compilation error when i tried to make a friend cout function: the compiler say "Error 4 error C2248: 'biumath::Assignment::m_rowsOfVarArray' : cannot access private member declared in class 'biumath::Assignment'". I thinks that the problem is with the namespaces.

biumath.h

#ifndef BIUMATH_H
    #define BIUMATH_H
    #include <iostream>
    #include <string>
    //using namespace std;

    namespace biumath
    {
    class Assignment
    {
    private:
        int **m_varArray;
        int m_rowsOfVarArray;
    public:
         Assignment(); //1
         Assignment(char symbol, double value); //2
         bool containsValueFor(char symbol) const; //3
         double valueOf(char symbol) const; //4
         void add(char symbol, double val); //5
        friend std::ostream& operator<< (std::ostream& out,
            const Assignment& assignment); //6
        };
    }
    #endif

biumath.cpp

#include <iostream>
#include "biumath.h"
using namespace biumath;
using namespace std;
std::ostream& operator<< (std::ostream& out,
        const Assignment& assignment)
{
        out<<assignment.m_rowsOfVarArray<<std::endl;
        //return the stream. cout print the stream result.
        return out;
}

again I cannot change the public part of the class. thanks!

why I cannot access the private member. I declared the function as a friend function — jhkhjkhj kjhhj, May 25 '15 at 15:35
@jhkhjkhjkjhhj: As explained in the duplicate, you've declared the friend to be in `namespace biumath`, then defined a different function in the global namespace. — Mike Seymour, May 25 '15 at 15:55

score 0 · Answer 1 · answered May 25 '15 at 15:14

0

Your error message explains the problem. The property m_rowsOfVarArray is declared as private, which means you cannot read from it or write to it outside of the class. To fix this, you need to change it to public or write an accessor function to retrieve the value.

answered May 25 '15 at 15:14

elixenide

44,308
16
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100

As I said I cannot chane the declaration of the public part of the class. and I can get to the private part, because the function is a friend funciton. – jhkhjkhj kjhhj May 25 '15 at 15:34

score 0 · Answer 2 · answered May 25 '15 at 15:18

0

You have to write or use a public method in order to change your variable. You use private to avoid any unexpected or unauthorised change of your variables. So, that only your public method is able to change it properly.

answered May 25 '15 at 15:18

holzkohlengrill

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19
29

error C2248 cannot access private member declared in class

2 Answers2

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