我必须做什么，该领域永久保存日期？

在我的小测试应用程序中，我使用领域保存用户的文本，但是当我停止应用程序并重新启动它时，数据就会消失 . 当我只是最小化应用程序或转到另一个视图而不是返回时，数据就在那里 .

这是我想要显示条目的TableView，带有添加条目的添加按钮 .

import UIKit
import RealmSwift

class MediUserlistViewController: UITableViewController {


    var userLists = try! Realm().objects(UserListClass).sorted("UserListName")

    override func viewDidLoad() {
        super.viewDidLoad()
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return userLists.count
    }


    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("UserListCell", forIndexPath: indexPath)
        let userList = userLists[indexPath.row] as UserListClass
        cell.textLabel?.text = userList.UserListName
        return cell
    }

    @IBAction func addList(sender: AnyObject) {
        let alertController = UIAlertController(title: "Neue Liste", message: "", preferredStyle: UIAlertControllerStyle.Alert)

        let saveAction = UIAlertAction(title: "Save", style: UIAlertActionStyle.Default, handler: {
            alert -> Void in
            let textField = alertController.textFields![0] as UITextField
            if(textField.text != ""){
                let realm = try! Realm()
                let newList = UserListClass ()
                newList.UserListName = textField.text!
                try! realm.write {
                    realm.add(newList)
                }
                self.tableView.reloadData()
            }
        })

        let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Default, handler: {
            (action : UIAlertAction!) -> Void in

        })

        alertController.addTextFieldWithConfigurationHandler { (textField : UITextField!) -> Void in
            textField.placeholder = "Name der Liste"
        }

        alertController.addAction(saveAction)
        alertController.addAction(cancelAction)

        self.presentViewController(alertController, animated: true, completion: nil)

    }
}

这是 class ：

import Foundation
import RealmSwift
class UserListClass: Object {
    dynamic var UserListName = ""
    let Medis = List<MediClass>()

    override static func primaryKey() -> String? {
        return "UserListName"
    }
}
ios swift realm