Make sure it looks like this. Also the simulator has to be set for 3.5inch as zbar's sdk doesn't support 4inch as of now. Thats actually what I am trying to fix now. If I find a fix I will post that back here as well.
#import "ZBarSDK.h"
@interface ReaderSampleViewController : UIViewController <ZBarReaderDelegate>
EDIT: Found the solution for 4 inch aka iPhone 5's here:http://www.federicocappelli.net/2012/10/05/zbar-library-for-iphone-5-armv7s/