On Sep 22, 2016, at 03:16 , Gabriel Zachmann <z...@tu-clausthal.de> wrote: > > That makes me wonder: why isn't it possible to register several, different > observers for the same thing? > That way, I wouldn't need to care about observations I didn't create, would I?
Because the observer is an object. Your observation and a superclass observation come from the same object. Whether these are to be treated as different observations** cannot be determined automatically, hence the need for a “context”. The reason it’s messy is that the observer/notification API is old and doesn’t follow modern API design practices. If this were being designed today, the “observeValueForKeyPath…” method would likely be replaced by a block/closure (similar to a completion handler) that’s passed as a parameter to the “addObserver…” call, and there wouldn’t be any contexts. ** That is, a superclass ‘addObserver’ may be in common code that’s used by all the subclasses, or it may be a private observation that’s separate from what subclasses use. Where the observation is created is insufficient to determine whether it’s an observation “you” created, or you “care about”. _______________________________________________ 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: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
