C++ - typeid(), used on derived class doesn't return correct type

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情话喂你
情话喂你 2021-01-05 02:22

Maybe I\'m misunderstanding how inheritance works here, but here\'s my problem:

I have a class Option, and a class RoomOption that derives from it. I have another cl

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  •  一向
    一向 (楼主)
    2021-01-05 03:25

    The typeid works differently for polymorphic (for classes having at least one virtual function) and non-polymorphic types :

    • If the type is polymorphic, the corresponding typeinfo structure which represents it is determined at run-time (the vtable pointer is commonly used for that purpose, but this is an implementation detail)

    • If the type isn't polymorphic, the corresponding typeinfo structure is determined at compile time

    In your case, you actually have a polymorphic class Option, but shared_ptr itsef isn't polymorphic at all. It basically is a container holding an Option*. There is absolutely no inheritance relation between Option and shared_ptr.

    If you want to get the real type, you first need to extract the real pointer from its container using Option* shared_ptr :

    Option * myPtr = player->getRoom()->getOption(0).get();
    cout << typeid(*myPtr).name(); << endl;
    

    Or alternatively (it is exactly the same thing) :

    Option& myPtr = *player->getRoom()->getOption(0);
    cout << typeid(myPtr).name(); << endl;
    

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