     func outlineView(_ outlineView: NSOutlineView,
                      objectValueFor tableColumn: NSTableColumn?, byItem item: Any?) -> Any? {
         switch item {
-        case is City:
-            let city = item as! City
+        case let city as City:
             return city.name
-        case is TimeOfDay:
-            let timeOfDay = item as! TimeOfDay
+        case let timeOfDay as TimeOfDay:
             return timeOfDay.title
-
         default:
             return "untitled"
         }

            //let city = item as! City
            //return city.videos[index]

        case is TimeOfDay:
            let timeOfDay = item as! TimeOfDay
            return timeOfDay.videos[index]

        default:

            }

            return view
        case let video as AerialVideo:
            let view = outlineView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "CheckCell"),
                                        owner: nil) as! CheckCellView   // if owner = self, awakeFromNib will be called for each created cell !
            // Mark the new view for this video for subsequent callbacks
