NSWiewController

I'm developing an application with a NSSplitView in the main NSWindowController which is organized like that:

a menu on the left panel, which contains an outlineView with many choices and a detailView on the right panel which corresponds to the item choosen in the left panel.

In the main NSWindowController, I have a toolbar with Buttons (that's the important point)

Then I click on an item in the left panel, I have the following action:

func outlineViewSelectionDidChange(_ notification: Notification) {
        let outline = notification.object as! NSOutlineView
        let item = outline.item(atRow: outline.selectedRow)
        if item is MenuSocietes {
            if vc != nil {
                splitView.removeArrangedSubview((splitView?.subviews[1])!)
                vc = nil
            }
            vc = societesController()
            contentViewController?.presentAsModalWindow(vc)
            if splitView.subviews.count > 1 {
                splitView.removeArrangedSubview((splitView?.subviews[1])!)
            }
            splitView.addSubview(vc.view)
        } if item is MenuImmeuble {
            if vc != nil {
                splitView.removeArrangedSubview((splitView?.subviews[1])!)
                vc = nil
            }
            vc = immeubleController((item as! MenuImmeuble).id)
            contentViewController?.presentAsModalWindow(vc)
            if splitView.subviews.count > 1 {
                splitView.removeArrangedSubview((splitView?.subviews[1])!)
            }
            splitView.addSubview(vc.view)
        } else {
            if vc != nil {
                splitView.removeArrangedSubview((splitView?.subviews[1])!)
                vc = nil
            }
        }
    }

Of course this is just a example (a little dirty, I know).

societesController and immeubleController are NSViewControllers.

Now I want my detailView (in the above code, societesController or immeubleController) to interact with the NSToolbar of the main NSWindowController.

It would be easy to pass this toolbar as a parameter in the init code of my details NSViewController, but I'm not sure it's the finest way.

I try to find, in my viewControllers (societesController and immeubleController) the ancestor, doing something like this:

var _parent = presentingViewController
        while _parent != nil {
            Swift.print(_parent?.className)
            _parent = _parent!.parent
        }

the first line return nil as _parent. Am I missing something?