Question

I have one header file which uses a virtual function.

This is declared and defined:

#ifndef HeaderH
#define HeaderH

class Base {
<some code>  
public:virtual int checkVal(int& val) { return val;} 
};
#endif

I have another header file which declares some functions, and inherits from this base header.

Finally, I have the implementation of this header file in another .cpp file:
I want to override the virtual function checkVal in my implementation here, but I keep getting a redefinition error.

int Base::checkVal(int&  value)
{
  if(value == 0)
        value = 10;
  return value;
}

Is there something I should include in my header file which will override the Base virtual function?

Answer 1

You have already provided the definition of checkval() inside your base class, so why are you redefining it? You can define it only once.If you want to give the implementation inside the .cpp file, just declare checkval() inside the base class, no need to define it there.

Your implementation of checkval() fails if you call it like the following:

Base b;
//some code
b.checkval(10);//Error because temporaries cannot be bound to non-constant references

Is there something I should include in my header file which will override the Base virtual function?

Create a derived class inside the header file and override checkval() then by declaring the function inside the derived class and defining it inside .cpp file.