I'm still relatively new to Pharo and to Smalltalk in general, and I've hit a situation where I'd like a model that notifies dependent views when it changes. Classically, it looks like this was done through #addDependent:, #update, #changed, #release and friends. I don't need more than a symbol message and an associated object, so I could live with that API, but I don't quite understand #release. It sounds like originally Object class held (non-weak) references to all objects that had dependents, so unless the dependents were explicitly released, the objects would never be released. I get the impression that at some point this was switched to using weak references, so I wouldn't have to worry about closed parent/dependent loops, but I can't find this explicitly spelled out anywhere. - Question 1: Does the basic addDependent/etc. system on Pharo use weak references? - Question 2: Am I correct in understanding that the main point of the Model class was to avoid having an entry in the Object class variable, so a closed parent/dependent loop could be garbage collected? - Question 3: If Pharo uses weak references, is there any point to the Model class? I've also seen some references to the Announcements framework, but I can't find as much documentation on it as I can on the "basic" Smalltalk dependency mechanism. It seems a bit more complex, with actual event classes, but I've not understood it yet. - Question 4: Should I prefer using Announcements for even mostly trivial cases? - Question 5: What benefits would Announcements give me? Any overall pointers would be appreciated as well. Thanks, Johann