Invoked when the formatter for the cell belonging to
control (or selected cell) rejects a partial string a user is typing into the cell.
- macOS 10.0+
The control whose cell rejected the string.
The string that includes the character that caused the rejection.
A localized, user-presentable string that explains why the string was rejected.
You can implement this method to display a warning message or perform a similar action when the user enters improperly formatted text.