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.

/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS2.0.sdk/System/Library/Frameworks/CoreGraphics.framework

http://discussions.apple.com/thread.jspa?messageID=7331891