Re: inheritance headache....

I have a construction problem that I need to fix;

currrently the following hierarchy exists;

       abstractTarget
       / \
      / \
 conreteTarget1 concreteTarget2

       abstractDescription (this class family can NOT be modified)
         / \
   concreteDesc1 concDesc1

Now somewhere, actually EVERYWHERE in this legacy code I see
statements like this;

// semi pseudo with
abstractTarget* createTarget(abstractDescription* desc)
{

// shortcut pseudo code for dynamic cast< > ()
   if ( desc is concreteDesc1)
   {
     return new concreteTarget1();
   }
   else if (desc is concreteDesc2)
   {
     return new concreteTarget2();
   }
   else
   {
     return 0;

   }

}

Now I CANT add methods to abstractDescription, if I could I would have
a method;

class abstractDescription
{
  AbstractTarget* create(AbstractDescription* desc)
  {
      desc->create();
  }

}

and each ConcreteDescription subclass would override as needed the
create the right concreteTarget.

BUT I cant do that as the AbstractDesciption family of objects cannot
be modified in any way. Can anybody help me out?

Im trying to tease out a solution here but I always get stung with a
cast or such like. anybody out there have any ideas?