On Thu, 2009-03-05 at 21:32 -0800, Andreas Raab wrote:
> Folks -
> 
> While doing some preferences stuff I ran into one of my "most-hated" 
> issues in Squeak. Anyone who has ever encountered SystemChangeNotifier 
> must have noticed how terrible it is to use it. I mean, just look at 
> this code:
> 
> prefEvent: anEvent
> 	"Check if this system event defines or removes a preference."
> 	(anEvent itemKind = SystemChangeNotifier classKind and: [anEvent 
> isRemoved]) ifTrue:[...].
> 	anEvent itemKind = SystemChangeNotifier methodKind ifTrue:[
> 		(anEvent isRemoved or:[anEvent isModified]) ifTrue:[...]
> 		(anEvent isAdded or:[anEvent isModified]) ifTrue:[...]
> 	].
> 
> just needless, pointless lines of case statements. How do people feel 
> about replacing that mess with Announcements? If you really want to have 
> all events you register for SystemEvent and if you'd like to be more 
> specific you go for more specifically for ClassEvent or even more 
> specifically for ClassAddedEvent. It would also remove the need for all 
> of these weird tests like
> 
> 	anEvent itemKind = SystemChangeNotifier methodKind and:[anEvent isRemoved]
> 
> and just replace them with something like "anEvent isMethodRemoval". It 
> would likely be faster too, since most places aren't really interested 
> in *all* events either.
> 
> It would mean that Announcents would have to go core but this cleanup 
> alone seems worth it. I also suspect that adding Announcements and 
> fixing SystemChangeNotifier may remove more code than it would add.
> 
> How do people feel about that?
> 
It sounds really good. I use Announcements for most of my stuff because
you can have specific dependencies that don't need any monkey patching.
I didn't know SystemChangeNotifier but while you are hunting I want to
point you to EventManager which might be replaced after Announcements
found their way into the image.

Norbert