Swift - Why is argument item in NSOutlineView always nil?

Question

I am attempting to implement a simple sourceView, however, I am only managing to set the stringValue of one textField.

First, this is the structure of my program:

class MainWindowController: NSWindowController, NSOutlineViewDataSource, NSOutlineViewDelegate
{
    @IBOutlet weak var sourceView: NSOutlineView!
    override func windowDidLoad()
    {
        sourceView.setDataSource(self)
        sourceView.setDelegate(self)
    }
}

Then, I have:

func outlineView(outlineView: NSOutlineView, numberOfChildrenOfItem item: AnyObject?) -> Int 
{...}

And finally,:

func outlineView(outlineView: NSOutlineView, child index: Int, ofItem item: AnyObject?) -> AnyObject
{...}

My issue is that in both of these functions, the value of item is nil. Is this what is supposed to happen?

Answer 1

It doesn't appear you're providing the object value. Unless you're using an NSTreeController to populate your NSOutlineView, you must also implement the data source function:

func outlineView(outlineView: NSOutlineView, objectValueForTableColumn tableColumn: NSTableColumn?, byItem item: AnyObject?) -> AnyObject? {

    // return your object value
}