NSDocument ViewController Hooks

DocumentViewControllerExtension.swift

extension NSViewController {
    
    var document: AnyObject? {
        if let target = self.parent, target.responds (to: #selector(getter: self.document)) {
            return target.perform(#selector(getter: self.document)) as AnyObject?
        }
        return self.view.window?.windowController?.document
    }
    
    var managedObjectContext: NSManagedObjectContext? {
        return (document as? NSPersistentDocument)?.managedObjectContext
    }

}