Unfortunately, there is not a practical example given for the use of the ActionSheet in the book. The call for the ActionSheet should be in whatever method needs the responses. iCal on iPad uses them, for example, when changing repeating events.
the -(void)actionSheet… method is a delegate method and should be in whatever file you have made the delegate of the actionSheet. Make sure that the file conforms to the delegate protocol.
I don't have this book, but the project was in an earlier book by the author, so I am not sure what you mean by
doesn't work on iPad. It does. It may not always be called when you start the program, (it will be the first time the program is run) since the program maintains the state it was in when you last left it. This is tied into the introduction of multitasking. My post on December 15 in this thread
Chapter 4 - Switching Views
offers a little more explanation, and points to some useful info in the documentation.
Also, not clear what you mean about changing -viewDidLoad into an IBAction method.