Invoked when the insertion point leaves a cell belonging to the specified control, but before the value of the cell’s object is displayed.
- macOS 10.0+
The control whose object value needs to be validated.
The object value to validate.
YES if you want to allow the control to display the specified value; otherwise,
NO to reject the value and return the cursor to the control's cell.
This method gives the delegate the opportunity to validate the contents of the control’s cell (or selected cell). In validating, the delegate should check the value in the
object parameter and determine if it falls within a permissible range, has required attributes, accords with a given context, and so on. Examples of objects subject to such evaluations are an
NSDate object that should not represent a future date or a monetary amount (represented by an
NSNumber object) that exceeds a predetermined limit.