When you file in code that defines a class that already exists, such that a new version of the class is created, it does not automatically recompile the subclasses of this class. Any subclasses continue to be subclasses of the previous version of the class.
The Hierarchy Browser, however, reports that the superclass of the class is the new version, and displays the new version of the superclass. This can be confusing if the protocol in the superclass is different, since methods in the new superclass version will not be understood.
Last updated: 7/13/16