UIViewController的InterfaceOrientation已弃用且Document建议使用[[UIApplication sharedApplication] statusBarOrientation],但iOS 8的扩展中没有sharedApplication.
正如@Retro所提到的,在大多数情况下,您可以使用self.traitCollection.verticalSizeClass或self.traitCollection.horizontalSizeClass在UIViewController中获取方向信息.