Hello, I'm playing with notification in MacRuby but I don't know the behavior of the same thing in Objc is a little diferent. I believe the problem could be something related to Macruby's XCode template that don't do something that the normal cocoa do. The app is really simple and I just created a new MacRuby app: 1º added the AddressBook framework in the target 2º in rb_main.rb I added: framework 'AddressBook' 3º in Interface build I dropped an ABPeoplePicker 4º created an new class called PeoplePickerViewController 5º made an NSObject in IB and set the class to my new controller 6º made an outlet to the ABPeoplePicker 7º add awakeFromNib and register an observer for notification. Everything goes and compile but the selector registered in notification is not called when user interact with ABPeoplePicker. I followed the same steps in pure Objc app and everything worked very well. Here is my Ruby code: https://gist.github.com/782006 (and the app http://cl.ly/42CZ) Here is my Objc code: https://gist.github.com/782007 Probably is something that I don't know how to do in MacRuby and is different from Objc. Someone could help? Thanks a lot.