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From: andrewjp@farcomp.UUCP (Andrew Peterson)
Newsgroups: comp.lang.c++
Subject: Re: Is there a way to tell which derived class an object belongs to?
Message-ID: <138@farcomp.UUCP>
Date: 1 Feb 90 01:20:48 GMT
References: <2815@draken.nada.kth.se>
Reply-To: andrewjp@farcomp.UUCP (Andrew Peterson)
Organization: Farallon Computing Inc. Berkeley, CA
Lines: 25

matsl@nada.kth.se asks whether there's a way to tell what subclass
of a baseclass an object is.  In other words, is there a method to
return the class of an object.  Clearly the answer is no.

As you probably know, most other object-oriented systems have 
such a mechanism, and it's easily put into C++ where it's needed.
Simply define a base class:
class MyBase {
	short type;
public: GetType( short ); SetType( short ); };

Use this base class as your base class.  Assign each class you're interested 
in an id (in a common header file), and in the constructor for the object,
call the SetType method.

Obviously this is a bit clunky, but it should work fine.  Apple's MacApp
provides such functionality in their base class TObject, including functions
to compare objects and find all the subclasses or superclasses.

I believe Objective C uses a similar naming scheme.

Andrew

apple!farcomp!andrewjp