A Boolean value that indicates whether the cell has a valid object value.
- macOS 10.0+
The value of this property is
true if the cell has a valid object value or
false if it does not. A valid object value is one that the cell’s formatter can "understand." Objects are always assumed to be valid unless they are rejected by the formatter. Invalid objects can still be accepted by the delegate of the cell’s
NSControl object (using the
control(_: delegate method).