[news.eclipse.tools.emf] Re: DataBinding + Validation Framework

["Will Horn" <will.horn@xxxxxxxxx>]

"Matt Biggs" <zebbedi@xxxxxxxxx> wrote in message 
news:08ca3e8b87dc55ffa55286e5166798ac$1@xxxxxxxxxxxxxxxxxx
> Could someone point me in the right direction or advise if its possible to 
> get EMF databinding to use the EMF validation framework as its source for 
> determining validation failures etc?
I've been looking into this recentely as well.

> All of the examples explain how to write your own IValidator however this 
> seems like im duplicating alot of code thats already within my model 
> validator.
Some types of databinding validation are not duplications of model 
validation, e.g. if you bind a Text widget to a numeric attribute, you need 
to validate that the string is numeric before you can event set it on the 
model.  But I agree that for most things like required attributes, valid 
ranges, cross attribute constraints, it is nicer to implement them at the 
model level where they can be reused outside of databinding.

> Similarly writing my own IValidator that calls a Diagnostician i guess 
> would work, however i wondered if this could be quite heavyweight?
I think this is the direction you have to go.  I'm considering using the EMF 
Validation Framework (the other one 
http://help.eclipse.org/ganymede/topic/org.eclipse.emf.validation.doc/references/overview/ValidationOverview.html) 
instead of Diagnostician because it is more configurable and extensible.  It 
can do fine grained validation (against a single change Notification) and 
reports problems as IStatus directly.  I'm also thinking it may prove easier 
to work with a ValidationStatusProvider rather than an IValidator.  For 
instance, UpdateValueStrategy works with and afterGet, afterConvert, and 
beforeSet validator, but doesn't have the notion (as far as I can tell) of 
an afterSet/model level validator.  ValidationStatusProvider (see 
MultiValidator for an example) looks like the way to handle validation once 
the target->model update has finished.

I'll follow up if I make any more progress.

-Will