Re: dynamic_cast is ugly!

From:

Juha Nieminen <nospam@thanks.invalid>

Newsgroups:

comp.lang.c++,comp.object

Date:

Wed, 12 Mar 2008 13:39:18 +0200

Message-ID:

<47d7c151$0$15005$4f793bc4@news.tdc.fi>

Daniel T. wrote:

Don't try to *do* things to objects. Objects are supposed to do for
themselves, clients *notify* the objects of things, they don't order
them around.

  How exactly do you propose to do that? Perhaps have a virtual function
in the base class like:

virtual void performAction(const std::string& action,
                           const std::string& parameters);

and then have the derived classes parse those parameters?

  I think I prefer dynamic_cast.

I can only think of one possibility: Clutter the 'Shape' base class
with Square-specific virtual functions. This defies all good OO
design.

What is it you are trying to tell squares that you don't want any other
shapes to know about? Why the big secret?

It's not like they must not know about it. It's just that it can be
something which only Square can rationally implement. The others have no
rational use for that functionality, and it would only be useless
clutter for their public interface to have such a function (which does
nothing).

As for an abstract "perform this action if you support it" function
like above... No thanks? For one, it's quite inefficient.