title: 'UINavigationController?' does not have a member named 'popToRootViewControllerAnimated'
body: <p>Please help me to find out what's going wrong in my code.</p>
  
  <pre><code>@IBAction func done(sender: AnyObject) {
  
      let moc:NSManagedObjectContext = SwiftCoreDataHelper.managedObjectContext()
  
      let predicate:NSPredicate = NSPredicate(format: "identifier ==  
                                  '\(contactIdentifierString)'")
      let results:NSArray = SwiftCoreDataHelper.fetchEntities(NSStringFromClass(Contact), withPredicate: predicate, managedObjectContext: moc)
  
      let contact:Contact = results.lastObject as Contact
  
      var toDoItem:ToDoItem = SwiftCoreDataHelper.insertManagedObject(NSStringFromClass(ToDoItem), managedObjectConect: moc) as ToDoItem
  
      toDoItem.identifier = "\(NSDate())"
      toDoItem.dueDate = datePicked
      toDoItem.note = titleTextField.text
      toDoItem.contact = contact
  
      SwiftCoreDataHelper.saveManagedObjectContext(moc)
  
      self.navigationController.popViewControllerAnimated(true)
  
  }
  
  func saveContext () {
      var error: NSError? = nil
      let managedObjectContext = self.managedObjectContext
      if managedObjectContext != nil {
  // here is problem (-2/completed/ContactU/ContactU/AppDelegate.swift:54:33: 
  // Cannot invoke '!=' with an argument list of type '(NSManagedObjectContext,  
  //  NilLiteralConvertible)')
          if managedObjectContext.hasChanges &amp;&amp; !managedObjectContext.save(&amp;error) {
              // Replace this implementation with code to handle the error  
              // appropriately.
              // abort() causes the application to generate a crash log and  
              // terminate.  
             // You should not use this function in a shipping application,  
             // although it may be useful //during development.
              //println("Unresolved error \(error), \(error.userInfo)")
              abort()
          }
      }
  }
  
  // #pragma mark - Core Data stack
  
  // Returns the managed object context for the application.
  // If the context doesn't already exist, it is created and bound to  
  //   the persistent store coordinator for the application.
  var managedObjectContext: NSManagedObjectContext {
      if !(_managedObjectContext != nil) {
          let coordinator = persistentStoreCoordinator
          if coordinator != nil {
              _managedObjectContext = NSManagedObjectContext()
              _managedObjectContext!.persistentStoreCoordinator = coordinator
          }
      }
      return _managedObjectContext!
  }
  </code></pre>