UIViewController is a UIResponder... but it's not the UIResopnder that should receive the insertText: message. You want to call insertText: on the UITextField itself. If you take a look at UIResponder.h you'll see the following comment near the paste: method
// these methods are not implemented in NSObject
Meaning that it's not necessarily safe to call them on just any UIResponder. They can only safely be called on subclasses such as UITextField and UITextView which actually implement them. This was a really strange design decision on Apple's part.
ragfield
2010-05-15 22:30:52