Overloading a virtual function in a child class

Question

I am just testing with virtual keyword and inheritance concepts in c++. I have written a small program:

#include<stdio.h> #include<iostream>  using namespace std;  class cna_MO {   public:     virtual void print()     {         cout << "cna_MO" << endl;     } };  class cna_bsc:public cna_MO {   public:     void print()     {         cna_MO::print();     }      void print(int a)     {         cout << "cna_BSC" << endl;     } };  class cna_Mo {     cna_MO *_mo;    public:     cna_Mo()     {         _mo = new cna_bsc;     }      virtual void print(int a)     {         cout << "cna_Mo with arg" << endl;         _mo->print(5);     }      virtual void print()     {         cout << "cna_Mo" << endl;         _mo->print();     } };  int main() {     cna_Mo valid_mo;     cout << "old case is started" << endl;     valid_mo.print();     cout << "new case is started" << endl;     valid_mo.print(5);     return 0; } 

What I have done here is I have overloaded a virtual function in parent class in child class! Is this not the right thing to do?

I am getting the compilation errors as below:

"temp10.cc", line 45: Error: Too many arguments in call to "cna_MO::print()".

Answer 1

Once you overload a function from Base class in Derived class all functions with the same name in the Base class get hidden in Derived class.

Once you added the function cna_bsc::print(int a) to your derived class the function cna_MO::::print() is no longer visible to users of the Derived class. This is known as function hiding.

Solution: In order to make the hidden function visible in derived class, You need to add:

using cna_MO::print; 

in the public section of your derived class cna_bsc.

Good Read:

What's the meaning of, Warning: Derived::f(char) hides Base::f(double)?