2010/5/17 Václav Šmilauer <[email protected]> > > > Ok. So is the derived class object also a base class object? Exactly > > the same one? > > You can always cast derived object to an instance of its base class, > that is the interest of inheritance, actually one of the most basic > principles of object-oriented programming. > > Think of casting as changing point of view; a doctor can see his friend > as his friend, or as a concrete patient, or as an instance of generic > mankind species, depending on what he needs. > > That happens when you cast. static_cast<FrictPhys*>(..) says that now > you want to see that object as a pointer to FrictPhys (heaven with you > if the cast is invalid -- dynamic_cast will give you NULL which you can > check, static_cast will skip that check and give you a valid but > nonsense pointer, which will most likely lead to crash). > > The pointer is always exactly the same. You can try pointer comparison > on some data member: > > FrictPhys* fp=static_cast<FrictPhys*>(i->interactionPhysics.get()); > NormShearPhys* nsp=static_cast<NormShearPhys*>(i->interactionPhysics.get()) > assert(&(fp->shearForce)==&(nsp->shearForce)); > > (When you access shearForce, internally you access the NormShearPhys > where it is declared; it is the compiler's job to resolve that). > > HTH, Vaclav >
Thanks for explanation! Sorry for basic question. I knew about inheritance I didn't about static cast. I see it might also be quite dangerous. cheers, Chiara > > > > > _______________________________________________ > Mailing list: > https://launchpad.net/~yade-dev<https://launchpad.net/%7Eyade-dev> > Post to : [email protected] > Unsubscribe : > https://launchpad.net/~yade-dev<https://launchpad.net/%7Eyade-dev> > More help : https://help.launchpad.net/ListHelp >
_______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
