How to detect when NSTextField has the focus or is it's content selected cocoa

Question

I have a NSTextField inside of a NSTableCellView, and I want an event which informs me when my NSTextField has got the focus for disabling several buttons, I found this meth

Answer 1

Just in case, as a slight variation over the idea of @sam, we can observe NSWindow.firstResponder property itself, it's KVO-compliant according to the documentation. Then compare it with textField or textField.currentEditor() to figure out whether the field is focused.