I’m working with an NSOutlineView which has two columns. My dataSource supplies the outline view with a tree of items of a custom class which represents file types (that is, you initialise it with a UTI). The first column is the display name of the file type (e.g., “Source code”, “Interface Builder NIB document”, etc.). The second column is an NSPopUpButtonCell which is supposed to allow the user to pick a handler for the given document type (think of Xcode’s “File Types” preference pane, and you’re pretty much there).

I can generate an NSMenu for a given item in the tree, populated with options based upon the Launch Services database entries for the UTI, complete with the relevant application icon and and so on. In fact, the menu itself works wonderfully, populated by way of NSPopUpButtonCellWillPopUpNotification.

The problem is, try as I might, the cell when the menu isn’t popped up always contains precisely one of two things: either an empty string, or the default text for the cell, the former if the result of -handlerName on the item (the attribute assigned to the column) is non-nil, the latter otherwise.

Moreover, I’m manually calling -selectItem: on the NSPopUpButtonCell instance, which just seems Wrong. In contrast, the left-hand column, which is just an NSTextFieldCell, everything just works (although granted, all it’s got to do is read the value from the item and present it).

(Disclaimer: I’m fairly new at Cocoa UI stuff; I know Objective-C, and lots of other programming languages, but I’ve not a huge amount of experience of building Mac OS X UIs, so be gentle).