You need to use NSStringFromCGRect which will convert the CG structs into NSString, Refer below:-
NSLog(@"%@", NSStringFromCGRect(frame));
Also below are the following other functions which can be used for NSLog CG Structs as well:-
NSStringFromCGPoint
NSStringFromCGSize
NSStringFromCGRect
NSStringFromCGAffineTransform
NSStringFromUIEdgeInsets