In the Objective-C/Cocoa world, Operations are encapsulated using the Receptionist Pattern. http://developer.apple.com/library/mac/#documentation/General/Concep

In the Objective-C/Cocoa world, Operations are encapsulated using the Receptionist Pattern. http://developer.apple.com/library/mac/#documentation/General/Conceptual/CocoaEncyclopedia/ReceptionistPattern/ReceptionistPattern.html http://developer.apple.com/library/mac/#documentation/Genera... And Events are handled with a combination of Key-Value Observing and UI binding. http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/KeyValueObserving/KeyValueObserving.html http://developer.apple.com/library/mac/#documentation/Cocoa/... Controllers still exist but the design of a program is easier to reason about if everything that mutates data is pulled out of the controller. UI changes must be made on the main queue, but the above design helps pull out model changes, network requests, etc on to background queues.