关于iOS 在AppDelegate.m文件里请求返回的ViewController出现bug

//[self returnViewController];

(UIViewController*)returnViewController {

CGRect calendarFrame = CGRectMake(0, 0, 320, 568);
 calendarFrame.size.height -= 44;

CalendarViewController *calendar=[[CalendarViewController alloc]init];
 calendar.view.frame=calendarFrame;

return calendar;


}
 //bug
 *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UIViewController _loadViewFromNibNamed:bundle:] loaded the "CalendarView" nib but the view outlet was not set.'