Re: C2614: Inheritance question

From:
Ulrich Eckhardt <eckhardt@satorlaser.com>
Newsgroups:
microsoft.public.vc.language
Date:
Mon, 08 Oct 2007 14:30:20 +0200
Message-ID:
<ufkpt4-psk.ln1@satorlaser.homedns.org>
Jack wrote:

This will call CPerson::Create() and not the virtual function from
CSupervisor. If you had put a 'virtual' into the baseclass, this would
have called the derived class' version of Create(). Note that you can
only add a 'virtual' in derived classes and not remove it. If your
derived class doesn't have a 'virtual' the function is still virtual
if the baseclass has it!

This means I have to add "virtual" to both the base class and the
overrided methods and implement both of them to accomplish what I needed.
And Yes. the 2 create's are the same.


Wrong. If it is declared virtual in one class, it will remain virtual in all
derived classes, regardless of whether the 'virtual' is repeated there or
not.

I tried to declare a base class method with virtual, if it doesn't exist
in code, it would cause a linkage error. So I put "virtual" in each of
them. Am I correct?


No, the distinction is between a virtual function and a pure virtual
function. The latter is declared with '= 0' at the end and doesn't have to
be implemented. Otherwise, you should always implement functions when you
also declare them, even though a non-virtual function that is not used will
not cause linker errors when not implemented.

Uli

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