I followed the book and I had difficulties! Most new examples seemed to add the code to viewcontroller and not appdelegate. It just has Quiz as a folder and appdelegate and viewcontroller not quiz as a prefix. It aborted using your code but more disturbing no way was I able or aware of -init executing and building the two NSMutable arrays.
I added the itiialization code in viewdidload for ViewController and it worked fine! How was -init supposed to initialize from QuizAppDelegate because currently it is not invoked no matter where I moved it! Many Thanks!