According to iOS\'s Using and Creating Error Objects, one can display a error object with the following code.
NSError *theError = nil;
BOOL success = [myDoc
Its in the AppKit framework. NSAlert
Import that framework to your project in xcode, then use the #include directive at the top of your code
there are also some samples of using NSAlert if you go to that page and look at the "Sample Code". I always do that if I'm unsure of any part of a new framework