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Re: [Gnumed-devel] Widgets talking to business objects

From: Karsten Hilbert
Subject: Re: [Gnumed-devel] Widgets talking to business objects
Date: Wed, 28 May 2003 13:30:49 +0200
User-agent: Mutt/

>> That makes sense, of course. What you are saying is that every
>> widget that accepts user input should have a dictionary
>> attribute self.widget_data for easy access to it's content so
>> that outsiders don't need to walk the input field tree ? And
>> Sians PropertySupport would be one way of automatically
>> pushing input field content into that dictionary ?
> Yes, but I would choose a different name.
You mean a name different from the Java lingo PropertySupport ?
I couldn't agree more ...

> No reason why the load () and save () methods can't talk to several
> business objects.
Sure. I just wanted to make sure that GUI plugins talk to
business objects (be they client, middleware or server-side)
and not directly to the persistence mechanism.

> > 2) upon *losing focus* the input field updates it's associated
> >    business object's data field - whether that be achieved by
> >    some clever generic mechanism similar to PropertySupport or
> >    by explicitely defined associations executed in a
> >    wxValidator is another matter
> This is difficult to generalise. It would mean writing a handler for
> each and every widget.
True. It would at least mean associating a business object
slot with each and every input field. The actual transfer can
be done generically, I suppose.

> Instead, they could load the dictionary, then
> we only need one handler, at the end, to talk to business object(s) and
> transfer the data.
Sounds fair.

>> 3) the business object temporarily persists state in, say,
>>    temp files (this idea also comes from Sians earlier
>>    postings) such that to be able to recover from client crash
> Plugins could save their dictionary easily.
Ah, I think I know what you are getting at ! You mean it's a
lot easier to just save widget state instead of business object
state because we then avoid the impedance mismatch (said
non-1:1-mapping between GUI and business objects) upon recovery
from backup files due to not having to recreate widget state
from business object state ? Surely easier technically. I
believe what Syan is currently working on in EditArea may over
time/several iterations lead to what we desire here.

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