Thanks everyone for your help on this, I found out my problem was how I was overriding -bind:toObject:withKeyPath:options:.
In my implementation when adding a view as an observer I neglected to add NSKeyValueObservingOptionOld to the options. Once I did that I was able to see the old values of the array. Thank! Mazen Abdel-Rahman On May 19, 2010, at 3:00 AM, Ken Thomases wrote: > On May 19, 2010, at 2:05 AM, Mazen M. Abdel-Rahman wrote: > >> I have a custom view class with an array property. I want to bind that >> array property to a model - which in my case is an array that is in a >> container/manager object. The binding is done via a custom view controller >> (in it's awakeFromNib). (calendar is the model object) >> >> [calendarView bind:@"events" >> toObject:calendar >> withKeyPath:@"events" >> options:options]; >> >> Now whenever "events" in the object calendar is modified "events" in >> calendarView is modified as well. >> >> In addition - observeValueForKeyPath... is getting called as well in the >> calendarView. >> >> The problem is that if some items are removed from calendar's (the model) >> "events array" by the time observeValueForKeyPath in calendarView gets >> called its "events" array has already been updated to reflect the model >> change. > > I think you have two options: > > * Override -bind:toObject:withKeyPath:options: and don't rely on the default > implementation, at all. > > * Use the default implementation but don't use > -observeValueForKeyPath:ofObject:change:context: to be informed about the > change of the view's property. Use the property's setter method, instead. > > > I would not expect that the view's property would already be updated at the > time that -observeValueForKeyPath:... is called, because by what mechanism > other than that method would the binding update that property? The answer, I > guess, is that the default implementation of -bind:... is actually setting > some other object (not the receiver) as the key-value observer of the key > path of the observableController, and that object is getting the > -observeValueForKeyPath:... message and then setting the property on your > view. However, if that's the case, I don't know why your view would have > -observeValueForKeyPath:... invoked on it, too. So, there's a bit of a > mystery there. And that's reason enough not to rely on the default > implementation -- it's a black box with ill-defined behavior. > > Overriding -bind:... is actually the method illustrated in Apple's > documentation about implementing a custom binding on a custom view. See the > "How Do Bindings Work?" section of the Cocoa Bindings Programming Topics. > > Also, have a look at the Sketch+Accessibility sample code, where it > implements custom binding (e.g. SKTGraphicView). It actually illustrates > both approaches. > > Regards, > Ken > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
