Re: c.d.theory glossary -- definition of "class"

From: Alan <alan_at_erols.com>
Date: Tue, 22 Jun 2004 16:36:47 -0400
Message-ID: <2jrjikF14rnj8U1@uni-berlin.de>

"Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message news:cba23f$vsv$1_at_news.netins.net...
> "mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message
> news:40d0aaa5$0$48959$e4fe514c_at_news.xs4all.nl...
> > --------------- " PUNTER: Good morning.
> > Glossary 0.0.4: RECEPTIONIST: Good morning, sir. Can I help you?
> > june 16, 2004 PUNTER: Well, I'd like to have an argument,
> >
> > --------------- please."
> > -- ARGUMENT SKIT - Graham Chapman & John Cleese
> >
> <snip>
> > [Class]
> > A class is what provides a name and a place for
> > the abstract behavior of a set of objects
> > said to belong to the class. (Larry Wall, Apocalypse 12)
> >
> > note:
> > Other definitons welcome, this goes for the rest as well,
> > of course.
> >
> > Some use 'class' as having exposed data.
> > Please be explicit about this if you do so.

>

> I really don't like the "A class is what ..." definition, especially since
> folks like Date keep asking why the OO folks are so confused on what a
class
> is -- is it a variable, for example? I would like to make it clear that
it
> is metadata. I don't just mean that the source code for the class is
> metadata -- the class is metadata. Here is a definition I just read in
> Systems Analysis & Design: An Object-Oriented Approach with UML by Dennis,
> Wixom, and Tegarden

>
> "A class is the template we use to define objects."

I agree. "Class" is often confused with "Instance" of a class. Class is the template, and the class is _instantiated_ when an object that belongs to that class is created. For example, we tend to forget that Windows is OO. A "text box" control that you place on a form is an instance of the "text box" class. This class has properties, which are in the template, many of which can be specified in the properties tab. The properties are specifiable for each instance of the class.

>
> This leaves the meatier definition to "objects" but at least it states
more
> clearly what a class is.

An object is an instance of a class or subclass. Received on Tue Jun 22 2004 - 15:36:47 CDT