Re: dynamic_cast is ugly!

From:
Juha Nieminen <nospam@thanks.invalid>
Newsgroups:
comp.lang.c++,comp.object
Date:
Thu, 13 Mar 2008 20:06:15 +0200
Message-ID:
<47d96d8a$0$8157$4f793bc4@news.tdc.fi>
dave_mikesell@fastmail.fm wrote:

std::vector<Drawable *> all_drawable_objects; // for the render loop
std::vector<Collidable *> all_collidable_objects; // for collision
detection

I only care about Collidables during collision detection. No need to
iterate over all objects and interrogate the type of each.


  In my case this solution doesn't work for two reasons:

  1) The order of the objects may change in the main container (and this
ordering is very relevant). I would have to maintain the same order in
the type-specific containers as well, which in some cases can become
exceedingly difficult. (Certainly more difficult than having to use
dynamic cast in a few places, so trying to do it becomes
counter-productive.)

  2) In some cases I have to traverse *all* the objects in the order in
which they are in the main container and perform *type-specific*
operations to them (iow. operations which cannot be specified as virtual
functions in the base class). It would not be enough to traverse the
type-specific containers one after another (because it would mean that
the objects are traversed out-of-order with respect to the main container).

  I actually am using your solution where I can (if for nothing else,
because it's more efficient, as less objects need to be traversed).
However, I can't do it in all cases.

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