How to get selected item of NSOutlineView without using NSTreeController?

Question

How do I get the selected item of an NSOutlineView with using my own data source. I see I can get selectedRow but it returns a row ID relative to the state of the outline. The only way to do it is to track the expanded collapsed state of the items, but that seems ridiculous.

I was hoping for something like:

array = [outlineViewOutlet selectedItems];

I looked at the other similar questions, they dont seem to answer the question.

Answer 1

NSOutlineView inherits from NSTableView, so you get nice methods such as selectedRow:

id selectedItem = [outlineView itemAtRow:[outlineView selectedRow]];

Answer 2

@Dave De Long: excellent answer, here is the translation to Swift 3.0

@objc private func onItemClicked() {
    if let item = outlineView.item(atRow: outlineView.clickedRow) as? FileSystemItem {
        print("selected item url: \(item.fileURL)")
    }
}

Shown is a case where item is from class FileSystemItem with a property fileURL.