Question

Edit: Thanks folks, now I see my mistake.

If I’m not wrong, because of its nature in factory method there is cyclic dependency:

Base class needs to know subclasses because it creates them, and subclasses need to know base class. Having cyclic dependency is bad programming practice, is not it?

Practically I implemented a factory, I have problem above, even I added

#ifndef MYCLASS_H
#define MYCLASS_H
#endif

I’m still getting

Compiler Error C2504 'class' : base class undefined

And this error disappers when I remove subclass include from base class header.

Answer 1

Solution 1: don’t #include the derived class headers in the base class header, only in the base class cpp. The declaration of the factory method should not use the type of concrete classes returned, only the base type.

Solution 2: use a separate factory class (or a factory method within a separate class) to create your objects. Then the cyclic dependency is totally eliminated. This is the preferred way.