Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!wuarchive!m.cs.uiuc.edu!ibma0.cs.uiuc.edu!ux1.cso.uiuc.edu!usenet
From: dmmg1176@uxa.cso.uiuc.edu (David M Marcovitz)
Newsgroups: comp.sys.mac.programmer
Subject: Think C polymorphism problem
Message-ID: <1991Mar6.233602.27014@ux1.cso.uiuc.edu>
Date: 6 Mar 91 23:36:02 GMT
Sender: usenet@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 39


I am using Think C 4.0 with TCL.  I have a superclass CFoo with
subclasses CBar and CBaz.  CFoo has the following methods:

void CFoo::MyMainMethod()
{
   TheAuxMethod();  /* Call an auxiliary method in CBar or CBaz */
}

void CFoo::TheAuxMethod()
{
   /* This is to be overridden by CBar and CBaz */
}
------------------------------------

CBar and CBaz have the following method:

void	CBar::TheAuxMethod()  /*substitute CBaz for CBar in CBaz.c*/
{
    /* Insert stuff that should get done. */
}
------------------------------------

When MyMainMethod is running (a method of CFoo), it calls
TheAuxMethod.  I don't want CFoo to have to know if the real object is
a CBar or CBaz object (i.e., I don't want some if structure to check
if I am a CBar and call CBar::TheAuxMethod or CBaz::TheAuxMethod).

I thought that by calling TheAuxMethod, the correct TheAuxMethod (from
the subclass, CBar or CBaz) would run.  That is not happening.  The
CFoo TheAuxMethod is getting called; it is not being overriden.

How can I call TheAuxMethod from one of CFoo's methods and have it be
overridden by CBar or CBaz's TheAuxMethod?

--
David M. Marcovitz                     |  internet: marcovitz@uiuc.edu
Computer-based Education Research Lab  |            dmmg1176@uxa.cso.uiuc.edu
University of Illinois                 |  novanet:  marco / cca / cerl