Re: Fix Virtual Base Class Pointer

From:
"Daniel T." <daniel_t@earthlink.net>
Newsgroups:
comp.lang.c++
Date:
Sat, 02 May 2009 19:07:58 -0400
Message-ID:
<daniel_t-231AED.19075702052009@earthlink.vsrv-sjc.supernews.net>
Immortal Nephi <Immortal_Nephi@hotmail.com> wrote:

     CommandMain derived class is derived from Command1, Command2, and
Command3 derived classes. Command1, Command2, and Command3 derived
classes are derived from robot virtual base class.
    I try to assign Robot Pointer to CommandMain. Then Run() function is
always invoked inside CommandMain derived class. How can you use
dynamic_cast? Dynamic_cast should be enabled to invoke Run() inside
either Command1, Command2, or Command3 derived classes.
    Please advise?

First, to answer your question directly, you need to dynamic_cast just
as you suspected:

void foo(Robot* aRobot)
{
   CommandMain* aCommandMain = dynamic_cast<CommandMain*>(aRobot);
   aCommandMain->Command1::Run();
   aCommandMain->Command2::Run();
   aCommandMain->Command3::Run();
}

I have to say though I think that this is extremely bad form. If you
have to do something like this, then your design is probably using
inheritance too extensively and inappropriately.

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