c++ Delete inherited member variable in child class

Question

Consider the following code:

Struct Base 
{
   int x;
   double y;    
}

Struct A : public Base
{   
}

Struct B : public Base
{  //here I don't want x (Base::x) to be inherited.
   // is there a way to delete it (something like delete Base::x)
}

Struct C : public Base
{   
}

What is considered best practice to achieve such a task? x should be inherited by A and C , (and maybe by many other classes) so I can't put it in the private section of Base . The only way I see is to remove x from Base and put it in A & C . But there should be another way right? Thanks.

Answer 1

There is no way to "delete" inherited data members, and you cannot even hide them. They get intrinsic part of the subclass. If B shall inherit just parts of Base , you need to split Base :

Struct Base 
{
   double y;    
}

Struct BaseWithX : public Base
{
   int x;
}

Struct A : public BaseWithX
{ }

Struct B : public Base
{ }

Struct C : public BaseWithX
{ }

Answer 2

Public inheritance makes an is-a relationship. That means B is a Base . And that means if Base has x then since B is a Base , B will have x . You need to re-think this design if you have that problem. Consider switching the relationship between B and Base to composition:

struct B {
    void some_function_using_base();
private:
    Base base_;
};

Answer 3

In terms of hiding a member of the base class, you can achieve that by inheriting privately from it and selectively exposing public (or protected) base class members using using :

Struct Base 
{
   int x;
   double y;    
}

Struct A : public Base
{   
}

Struct B : private Base
{  
   using Base::x; // only pull in x in the public section of the class
}

...

B b;
double y = b.y // <= compilation error here