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From: dslg0849@uxa.cso.uiuc.edu (Daniel S. Lewart)
Newsgroups: comp.lang.pascal
Subject: Re: TP5.5: Can't store method in procedure variable
Keywords: Method Object Procedure TP5.5
Message-ID: <1990Dec4.174837.24879@ux1.cso.uiuc.edu>
Date: 4 Dec 90 17:48:37 GMT
References: <1990Dec3.061013.22258@ux1.cso.uiuc.edu> <2218@mentor.cc.purdue.edu>
Sender: news@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 39

garlange@mentor.cc.purdue.edu (Mark Garlanger) writes:

> The question I have is WHY you would want to do this?  Methods are closely
> tied to the data structure associated with it.  What would you want the
> program to do with the method tries to access the data that the object has 
> defined?   What you are trying to do would cause many ambiguities for the 
> compiler.  I bet there is a way to solve your general problem by using
> the object-oriented programming directly, such as using virtual methods.
> I have done some work with objects and if you gave your general problem, I
> may be able to offer some hints on how to do it.

My intention is to use object methods in my menuing system.  For each entry in
a menu, there is a procedure which is executed when that entry is selected.
This works for ordinary procedures, but it won't even compile for object
methods.  The example I posted was constructed to illustrate my problem as
simply as possible.

I don't see how there would be any compiler ambiguities, but I do hope you win
the bet!

In practice, my code for initializing each entry in a menu looks like the
following (Name's are strings):
     AddItemProc( Name1, Proc1 );
     AddItemProc( Name2, Proc2 );
     ...
I would like one of these Proc's to be an object method:
     AddItemProc( Name3, Obj.Method );

Currently, I have to resort to the following code:
     procedure ObjMethod;
     begin
       Obj.Method;
     end;
     AddItemProc( Name3, ObjMethod );

Thank you for your kind offer,

Daniel Lewart
d-lewart@uiuc.edu


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