Message-ID: <31C63DA9.44B3@3-cities.com>
Date: Mon, 17 Jun 1996 22:24:57 -0700
From: "Travis Griggs (and Kerrin and Courtney too)" <tkc@3-cities.com>
Reply-To: tkc@3-cities.com
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Subject: Questions about System Dependency Events
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I have some questions about the SystemDependencyEvents application that 
now ships as an optional filein for VW2.5. To begin with - how true to 
the Digitalk generalized event model is it?

I like it and find it to be an improvement over the traditional 
DependentsFields mechanism found from ParcPlace for three reasons:
1) more robust (can have blocks and variable number of arguments, etc)
2) more semantically clear (when:send:to: at the object level instead of 
onChangeSend:to: for only subclases of ValueModel)
3) wider bandwidth possible (now trying to sort it all out with complex 
update: statements, or hooking up a gazillion dependency transformers)

Given that, does any one know what PPD's plan is for this stuff? Are 
they going to refit ValueModel so it sends

self triggerEvent: #value 

instead of

self changed: #value?

And so on and so forth?

And last of all for right now, why are the dependents/event handlers in 
either system bound to the triggering objects weakly? I've been using 
VisualWorks for four plus years now and this has always puzzled me? Why 
not just use WeakArrays/WeakDictionaries so that copious amounts of 
'release' code don't need to be written?

Travis Griggs
tkc@3-cities.com
