Alec Flett wrote:
John Anderson wrote:
Yes
in some cases we don't want any notifications. Consider this case:
wxWidgets handles the click, updates the selection on the screen and
tells us about the change. As a result we store the change in the
selection.
I think this is a broken paradigm in CPIA - If CPIA is really a MVC
paradigm, then the proper thing to do would be to update the model (by
setting the selection attribute) and letting the view reflect this
change (by actually telling the widget to select something)
Actually this isn't a CPIA issue, it's a platform issue. Consider the
case when a window changes size. The platform notifies us of the change
and we have to update the model, but we don't need to also change the
platform widget, its already up to date. The main thing to keep
straight is that event driven platform frameworks keep the widgets up
to date and all we need to do is reflect the change in the model. The
completely different situation occurs when the data changes and for
some reason the platform can't notice it. In that case we need to
update the model and synchronize the widget to the new value.
The problem is that we're trying to do BOTH: update the view and the
model manually, and then wishing the controller wasn't getting
involved. The reason for this is that we don't have complete control of
our widgets: when a user clicks the mouse, the widget wants to update
itself whether or not the model has actually changed.
This is the one thing that always seems to be vaguely defined in the
MVC
implementations I've worked with, including CPIA: proper downstream
(view -> model - maybe that's upstream? anyway..) communication.
My suggestion would be for the view (i.e. the widgets) to maintain some
sort of state about the fact that its changing an attribute (selection)
and then ignore notifications on selection. I don't think that
collection notifications should have to shoulder this burden because
its really proprietary to CPIA's design.
Yes, I\d like to ignore the notification. The problem is that I can't,
because some of the notificaitons are asynchronous.
Alec
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