I found the problem, It was in the IB... there was not a connection from the column textField to the table view cell.

I know how I am going to proceed. I will build an array that I will update from the ComboAction and then use this array for the tableView as opposed to try to update the tableView cells directly.

Thanks Claude, I used the @IBAction because I needed the contents of the comboBox and I had tried the delegate before and could not see a way to get contents of comboBox.

Thanks to Claude for getting this working..

I get an error when I added the following statement NSComboBoxCell.delegate = self The error was no delegate member for NSComboBoxCell.. So, I created a new test project which had a single view and a tableView that I added a comboBox to one of the columns without trying to use a datasource, I expected to see Item 1, Item 2 .. etc. in the column, but again nothing. Also, the comboBox is editable. There must be something basic I am missing. Still looking for an example..

I changed func numberOfItemsInComboBoxCell(in comboBoxCell: NSComboBoxCell) - Int { to func numberOfItems(in comboBoxCell: NSComboBoxCell) - Int { and the error went away, however it still does not work. Also, I put a breakpoint on the function " func comboBoxCell" and it does not get called. Any Ideas how to resolve?

It turns out if I use a NSTextView object instead of NSTextField object the spelling and grammar are built in. So, all I had do to was the following: create a scrollable text view object and then connect the TextView as follows:  @IBOutlet var itemDescription: NSTextView! Then turn on continuous spell checking with  itemDescription.isContinuousSpellCheckingEnabled = true