问如何使用addObserver激活通知

EN

init(modelName: String) {
    self.modelName = modelName
    setUpNotificationHandling()
  }

private func setUpNotificationHandling() {
     
    let notificationCenter = NotificationCenter.default
 
    if #available(iOS 13.0, *) {
      notificationCenter.addObserver(self, selector: #selector(saveChanges(_:)), name: UIScene.willDeactivateNotification, object: nil)
    } else {
      notificationCenter.addObserver(self, selector: #selector(saveChanges(_:)), name: UIApplication.willResignActiveNotification, object: nil)
    }
     
  }




@objc func saveChanges(_ notification: Notification) {
        
        saveChanges()
    }
    
    private func saveChanges() {
        guard self.managedObjectContext.hasChanges  else {
           
            return
        }
        
        do {
          
            try self.managedObjectContext.save()
        }
        catch {
            print("unable to save moc")
            print("\(error), \(error.localizedDescription)")
        }
    }