🚀 go-pugleaf

HELP! Suggestions are MOST WELCOME!

Why would someone use an enum for a class_ID in a class library? Why not
simply provide a GetClassID() function for each class? That would be so
much simpler and so much more useful!

I don't seem to be able to use the enum class_ID  to find out what class
an object is because class_ID isn't "virtual" like a function. If you have
an object of a class that is derived from a base class, and you are
referencing that object using the base pointer, then class_ID does not
tell you the class of the object, it tells you the class of the pointer.
What god is this? I know what class the pointer is because I cast it
myself! Duh?

This means that I don't seem to be able to create a routine that uses a
base class as a pointer to any of that base class's derived classes. . .
because in that routine I need to know exactly what the class_id is of the
REAL object rather than the class_ID of the base object (which is pretty
darn obvious because it never changes).

I did not expect to run into this problem. Is this a limitation? an error
on my part? Is there another way to find out the actual class of an object
without using a class_ID enum that really will give me the correct
class_ID?

So , by using an enum . . .whatever you type cast a pointer as. . . that's
the class ID that you get. . . so it isn't any better than a compiler
#define as far as I am trying to use it.

If you check out my code example below. . .you will see my confusion as to
why a class_ID enum would be used . . . and I hope ther is another way of
finding out an object's actual class ID.

PS: and no, it is not possible to give each class a GetClassID routine
because I am having this problem with the Metrowerks PowerPlant class
library and I don't think it is very acceptible to  just go around
changing the inner workings of a class library.

class LPane {
   public:
      enum { class_ID = 'pane' };
      LPane() {};
      ~LPane() {}; 
};

class LView : public LPane {
   public:
      enum { class_ID = 'view' };
      LView() {};
      ~LView() {};
};

void main (void) {
 LPane aPane;
 LView aView;
 LPane * aPanePtr = &aPane;
 LView * aViewPtr =  &aView;
 LPane * aPanePtr2 = (LPane*)aViewPtr;
 
 long aPaneClassID = aPanePtr->class_ID;    // = 'pane' (obviously) 
 long aViewClassID = aViewPtr->class_ID;    // = 'view' (obviously)
 long aWhichClassID = aPanePtr2->class_ID;  // = 'pane' ********* why?
**********
}

/*                                   
                                     ?
 ___  o     _             _         /
| o \ _ ___| |_ ___ _ _ _| |    /"""\
|   /| | __)   | o | '_| o |    |~'~|       
|_|_\|_\___)_|_|_|_|_| \___|    \ - /     
.---------------------------------^----. 
| Richard Jason Lyders  Houston, Texas |
|         richard@moriarty.com         |
'-----------------------------OOo----oOO
                                |=[]=|       
                                /_/\_\            
                               oOO  OOo

*/

      [ Articles to moderate: mailto:c++-submit@netlab.cs.rpi.edu ]
      [  Read the C++ FAQ: http://www.connobj.com/cpp/cppfaq.htm  ]
      [  Moderation policy: http://www.connobj.com/cpp/guide.htm  ]
      [      Comments? mailto:c++-request@netlab.cs.rpi.edu       ]