Question

我正在研究一个快速的3教程并且核心数据存在问题。在运行代码时我能够保存我的数据，我想，但是当我想将它加载到我的控件中时，我得到一个错误。 image of the app

这是我的代码：

lazy var managedObjectContext: NSManagedObjectContext? = {
   let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    return context
}()


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

@IBAction func speichernPressed(_ sender: UIButton) {
    writeData()
}

@IBAction func ladenPressed(_ sender: UIButton) {
    loadData()
}

func writeData() {
    let kontakt = NSEntityDescription.insertNewObject(forEntityName: "Kontakte", into: self.managedObjectContext!) as! Kontakte
    kontakt.vorname = vornameTextField.text!
    kontakt.name = nameTextField.text!
    kontakt.plz = plzTextField.text
    kontakt.ort = ortTextField.text!
    kontakt.strasse = straßeTextField.text!

    do{
        try managedObjectContext?.save()
    } catch {
    }
    showAlertViewWithTitle(title: "Hinweis", message: "Datensatz wurde gespeichert!")

    vornameTextField.text = ""
    nameTextField.text = ""
    straßeTextField.text = ""
    ortTextField.text = ""
    plzTextField.text = ""
}

func loadData() {
    let fetchRequest = NSFetchRequest<Kontakte>(entityName: "Kontakte")

    let predicate = NSPredicate(format: "nameTextField contains %@", nameTextField.text!)
    fetchRequest.predicate = predicate

    var fetchResults: [Kontakte] = []
    do {
        try fetchResults  = managedObjectContext!.fetch(fetchRequest)
            if(fetchResults.count > 0) {
                nameTextField.text = fetchResults[0].name
                vornameTextField.text = fetchResults[0].vorname
                straßeTextField.text = fetchResults[0].strasse
                ortTextField.text = fetchResults[0].ort
                plzTextField.text = fetchResults[0].plz
            }else {
                showAlertViewWithTitle(title: "Hinweis", message: "Datensatz nicht gefunden!")
            }
        }catch {
            showAlertViewWithTitle(title: "Fehler", message: "Bei der Verarbeitung ist ein Fehler aufgetreten!")
        }
}

func showAlertViewWithTitle(title: String, message: String) {
    let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "Schliessen", style: .default, handler: nil))
    self.present(alert, animated: true, completion: nil)
}
}

image after saving

错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'unimplemented SQL generation for predicate : (nameTextField CONTAINS "Lebowski")'

我很感激任何帮助

Answer 1

我通常做这样的事情

    var contacts = [Kontakte]()

例如在viewDidLoad

中

    let appDelegate = UIApplication.shared.delegate as! AppDelegate

    let managedContext = appDelegate.persistentContainer.viewContext

    let contactFetch = NSFetchRequest<NSFetchRequestResult>(entityName: "Kontakte")

    do {
        contacts = try managedContext.fetch(contactFetch) as! [Kontakte]
        // loop results
        for contact in contacts {
           print(contact.vorname)
        }

    } catch {
        fatalError("Failed to fetch contacts: \(error)")
    }

如何使用swift 3

1 个答案: