iphone changing view size on keyboard appearance

NSDictionary* info = [notification userInfo];

       CGSize keyboardSize = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;

        self.textNoteView.frame = CGRectMake(self.textNoteView.frame.origin.x, self.textNoteView.frame.origin.y, self.textNoteView.frame.size.width, self.textNoteView.frame.size.height - keyboardSize.height);