Question

class BaseA{}; , class DerivedB{}; class DerivedC{};

DerivedB can be derived from BaseA : Want to allow: class DerivedB: public BaseA

But, if someone tries to do DerivedC : public BaseA ==> want to restrict this.

Is it possible?

Answer 1

You can make all BaseA‘s constructors private and add DerivedB as a friend of BaseA‘s.

class BaseA
{
    friend class DerivedB;
private:
    BaseA();
};
class DerivedB : BaseA
{
};
class DerivedC : BaseA  //error - I get it when I try to create an object in MSVS
                        //but in principle it works
{
};