Question

I have a parent class “base” and another class “derived” that inherits from “base”.

“derived” has 1 method cH1.

if I do this:

base* b = new derived();

And I want to be able to do this:

b->cH1();

Obviously I can’t and there are 2 solutions:

• Either declare cH1 as pure virtual in base.

• or do this:

  dynamic_cast<derived*>(b)->cH1();
  

Which one is a better practice?

Answer 1

If cH1 method semantically applies to base, then make it a base‘s method.
Else, leave cH1 to derived, and use dynamic_cast.
I think the semantics of your classes should drive your choice.

For example, if you have a base class Vehicle and derived classes Car, Motorbike, and Aircraft, a method like TakeOff() has a semantics compatible with Aircraft but not with Car or Motorbike, so you may want to make TakeOff() an Aircraft method, not a Vehicle method.