Re: C2614: Inheritance question

From:
"Jack" <jl@knight.com>
Newsgroups:
microsoft.public.vc.language
Date:
Mon, 8 Oct 2007 19:18:32 +0800
Message-ID:
<#ylk1zZCIHA.4476@TK2MSFTNGP06.phx.gbl>

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. 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?
Thanks
Jack

Now, generally, you define an interface in the baseclass:

 struct CPerson {
    bool Create(...);
 };

In order to allow derived classes to implement/override this, you need to
declare this function virtual:

 struct CPerson {
    virtual bool Create(...);
 };

If there is no sensible default-implementation in the baseclass, you make
it
a pure virtual function:

 struct CPerson {
    virtual bool Create(...) = 0;
 };

Every derived concrete class then has to implement this function.

Uli

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