是否可以从AnyObject获取Self？举个例子://SuperclassclassManagedObject{classfuncfindByID(id:String)->AnyObject?{letobjects=objectsWithPredicate(NSPredicate(format:"id==%@",id))returnobjects.firstObject()//ReturnsAnyObject}}//SubclassclassUser:ManagedObject{classfuncreturnFirstSelf()->Self?{returnfindById("1")