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From: sho@maxwell.physics.purdue.edu (Sho Kuwamoto)
Newsgroups: comp.lang.c++
Subject: Re: Re^2: Is there a way to tell which derived class an object belongs to?
Message-ID: <3062@pur-phy>
Date: 5 Feb 90 06:55:11 GMT
References: <2815@draken.nada.kth.se> <636@tci.bell-atl.com> <7722@chaph.usc.edu> <645@tci.bell-atl.com> <133@dumbcat.UUCP>
Sender: news@pur-phy
Reply-To: sho@maxwell.physics.purdue.edu.UUCP (Sho Kuwamoto)
Organization: Purdue Univ. Physics Dept., W. Lafayette, IN
Lines: 33

In article <133@dumbcat.UUCP> marc@dumbcat.UUCP (Marco S Hyman) writes:
>In article <645@tci.bell-atl.com> kempf@tci.bell-atl.com (Cory Kempf) writes:
    >>>Is there any way you can tell which derived class an object belongs to
    >>>if it is pointed to by a pointer to its base class? 
    
    [method involving using a virtual member function returning a unique
    constant for each class deleted]
    
>Picture a common scenario:
> [someone screws up by forgetting to write down the number on a]
> [piece of paper.  the number is reused.  oops]

What I'd like to see:
1) A sort of extensible enum.  One you could add new members to 
   in separate .h files.

addEnum IDEnum {class1ID, class2ID, class3ID};
addEnum IDEnum {classXID, classYID};

I think this would be useful for many applications where a derived class
adds functionality to an older class.  

2) A "mandatory" virtual.  Every derived class *must* redefine this type
   of method.  This is not as useful, but there are a few instances
   (like this one) where each new class *must* redefine a method.

As if C++ weren't a kitchen sink language to begin with...

-Sho
--
sho@physics.purdue.edu  <<-- Now if only I could afford a C++ compiler
                             for my mac...  and Apple completely rewrote
                             their ROMs for it... and...