I've got an NSPopupButton where I bound the Content property to my array controller's arrangedObjects, with a model key path of 'name'. If I click on the popup, it correctly shows all of the names I expect to see. When I then select one of those names, nothing happens. The list goes away as expected, but the displayed name is still the first item in the list.
NSPopupButton won't change value
I had the same problem.
I change the type of button cell from pull down to pop up, and now it works fine.
Looks like a bug.
According to Managing Pop-Up Buttons and Pull-Down Lists this is expected behavior
Unlike popup lists, the title of a popup button displaying a pulldown list is not based on the currently selected item and thus remains fixed unless you change using the cell’s setTitle:method.