[Python-Dev] Oberver Pattern

Magnus Lie Hetland magnus@hetland.org
Wed, 15 May 2002 22:40:52 +0200

Fredrik Lundh <fredrik@pythonware.com>:
> magnus wrote:
> > > > This could be very useful for GUIs, too, for implementing
> > > > model-view relationships. The anygui people would be very
> > > > interested, I'm sure.
> > > 
> > > Indeed!
> > >
> > > have you actually built large-scale UI applications using a
> > > one-size-fits-all observer model, or are you just guessing?
> > 
> > Guessing about what?
> the "very useful for implementing model-view relationships"
> part, of course.
> since you didn't reply to the "large-scale" part, and gave an
> example that doesn't really have much to do with model-view
> design (unless you're writing a GUI builder, perhaps) I assume
> you're still mostly guessing.

Hey - lighten up... If you read my answer, I was replying to the "The
anygui people would be very interested, I'm sure" part. I was

The reason the Anygui MVC architecture is the way it is is mainly to
avoid the need for notification in every little modification; with
observable built-ins this sort of thing would have to be handled in
another manner, of course. I'm not sure exactly how this should be
done, but, as I said, I am interested.

> if you want something closer to real-life, consider how well a
> "standard observer" would deal with the following example:
> # load the model
> dom = xml.dom.minidom.parse(filename)
> # create a view
> mywidget = MyDisplayView()
> mywidget.show(dom)
> # modify the model
> for element in dom.getElementsByTagName("sometag"):
>     ...

I'm not sure I see your point here (although I'm sure it's entirely my
fault). Are you saying that there would be a problem because you would
get too many notifications? If so, I don't see how that's inherent in
being able to observe values belonging to built-in types (which is
what I'm interested in).

Oh, well. I guess it's not going to happen anyway, so this discussion
is probably going nowhere.

> </F>

Magnus Lie Hetland                                  The Anygui Project
http://hetland.org                                  http://anygui.org