func viewWillAppear (Bool)
Notifies the view controller that its view is about to be added to a view hierarchy.
それのビューがもうすぐあるビュー階層に加えられることをビューコントローラに通知します。
func viewDidAppear (Bool)
Notifies the view controller that its view has been added to a view hierarchy.
func viewWillDisappear (Bool)
Notifies the view controller that its view will be removed from a view hierarchy.