I attended interview for position for iOS on Sep 2013, first they took written, that was just basic like category, protocol, atomic Vs non atomic, new feature in iOS 6, delegation, tableview data source, inferitance, abstraction.
Then second round was Technical round where he asked about file system, polymorphism, new feature in iOS 7, profile for ios app, core data, NSOperationQueue.
Third round was again technical where he asked about data structure implementation in Objective C, distribution of iOS App, UITextView class hierarchy, compiler version.