How Can I Dynamically Switch Storyboard-Based Context Menus in NSOutlineView Based on Selection?

Below is an overview of two approaches you might take:

---

1. Updating the Existing Menu in menuNeedsUpdate

In your implementation of the NSMenuDelegate method

  menuNeedsUpdate(_:)
you cannot reassign the passed-in menu (it’s a constant), but you can modify its items. This means you might remove all items and insert the ones you need at that moment. For example:

SWIFTCopied
extension ViewController: NSMenuDelegate {
    func menuNeedsUpdate(_ menu: NSMenu) {
        // Remove existing items.
        menu.removeAllItems()

        // Based on your selection, add new menu items.
        if /* condition for menuOne */ {
            menu.addItem(withTitle: "MenuOne Action", action: #selector(doMenuOneAction), keyEquivalent: "")
        } else if /* condition for menuTwo */ {
            menu.addItem(withTitle: "MenuTwo Action", action: #selector(doMenuTwoAction), keyEquivalent: "")
        } else if /* condition for menuThree */ {
            menu.addItem(withTitle: "MenuThree Action", action: #selector(doMenuThreeAction), keyEquivalent: "")
        }
    }
}

In this approach you build just one menu (set in Interface Builder) but update its contents dynamically. This doesn’t “switch” the NSMenu object, but it achieves the dynamic behavior you need.

---

2. Returning a Different NSMenu by Subclassing NSOutlineView

If you prefer to swap out entire menus rather than updating items in place, you can subclass NSOutlineView and override its

  menu(for:)
method. However, since your IB outlets (menuOne, menuTwo, etc.) are in your view controller, you’ll need a way to get to them from your outline view. One common strategy is to have the view controller set a weak reference on the outline view after it’s loaded. For example:

SWIFTCopied
class MyOutlineView: NSOutlineView {
    // Add a property to hold a reference to the view controller.
    weak var owningViewController: ViewController?

    override func menu(for event: NSEvent) -> NSMenu? {
        // Determine which menu to show based on the selection.
        guard let vc = owningViewController else {
            return super.menu(for: event)
        }
        
        // Example: decide based on the currently selected row.
        if /* condition for menuOne */ {
            return vc.menuOne
        } else if /* condition for menuTwo */ {
            return vc.menuTwo
        } else if /* condition for menuThree */ {
            return vc.menuThree
        }
        
        return super.menu(for: event)
    }
}

Then in your view controller’s awakeFromNib or viewDidLoad, connect the outline view’s reference:

SWIFTCopied
class ViewController: NSViewController {
    @IBOutlet weak var myOutlineView: MyOutlineView!
    
    @IBOutlet var menuOne: NSMenu!
    @IBOutlet var menuTwo: NSMenu!
    @IBOutlet var menuThree: NSMenu!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        myOutlineView.owningViewController = self
    }
}

This way, your NSOutlineView subclass can access the menus that you’ve set up in your storyboard via outlets on your view controller.

---

Summary

• If you’re happy with modifying the menu’s items on the fly, use the NSMenuDelegate’s menuNeedsUpdate(_:) method to update the existing menu.
• If you really need to swap out the entire menu object, subclass NSOutlineView and override menu(for:). To access your IB outlets from there, have your view controller assign itself (or just its menus) to a property on the outline view (via the responder chain or a manual assignment in viewDidLoad).

Both solutions are viable; your choice depends on whether you prefer modifying a single menu’s contents or swapping out menu objects entirely.