I am trying to set my UITextView as the first responder with [self.textView becomeFirstResponder] when my view controller called viewDidAppear. But sometimes it will cause crash with the error: [__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[0] all I did is just: - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; [self.textView becomeFirstResponder]; } So if anyone can tell me what happened and how to do? when I call the [self.textView becomeFirstResponder], what will be insert into the responders list? self.textView itself? Thanks very much!