While trying to teach myself iPhone development I refer to the reference help material a lot. They always want you to use a thing
CGRrectZero but you will get this error.
"_CGRectZero", referenced from: _CGRectZero$non_lazy_ptr in CouponController.o ld: symbol(s) not found
To fix the error you must add “CoreGraphics” to your frameworks in XCode. To do that right click your “Frameworks” folder, add “Existing Framework”, then find CoreGraphics.framework.