I have a Mac app that uses NSOutlineView in the app's sidebar, which has collapsible 'sections' of items in the sidebar (like in the Apple Music app). It works with regular NSOutlineViewDataSource but I was having a few issues with the implementation, and I was considering replacing that with a DiffableDataSource. However, when initializing `NSTableViewDiffableDataSource', I can't pass in a NSOutlineView. I just want a table view with 'sections' that can be used in the Mac app's sidebar.

Hi. Would this be required even if I don't have a 'custom type' to define in my app? I just have a list of files with their URLs on disk that I want the user to be able to drag out to Finder. Everything works fine for dragging out to other apps (like Mail, Notes), but not to Finder. In this case, is there a general file extension or MIME type that I would add?

Hi. That doesn't explain why the subview version works fine on iOS, but is very slow on macOS. Also, the branching is the same in both cases.

I tried that ... now the focus notifications work, but while typing in the TextField, pressing spacebar doesn't work; it always seems to trigger the Button action handler instead.

This is for a macOS (AppKit) app, so I'm testing it on a Mac.

Thanks. That's what I'm going with right now