Enabling NSButton with bindings, based on NSTableView selection

Question

I have a NSWindow containing an NSButton and an NSTableView.

I'd like the button to be enabled if and only if the table contains at least one item, and exactly one item is selected. (The table does not allow multiple selection.)

What can I bind the button's enabled binding to to make this happen?

Answer 1

Try this: (Not tested.)

Answer 2

Try binding to the array controller's selectedObjects, model key path count, with no value transformer.

Note that this would be unsafe if you allowed multiple selection: For one thing, the count could easily be neither YES nor NO; for another, if the user selected a multiple of 256 items, the lowest byte of the count would be 0, so the BOOL value would be NO even though there is a selection.