ios - Swift:删除核心数据，表不会更新

Question

此代码似乎正在删除实际数据，但没有行，表不会更新，除非我强制关闭应用程序并重新打开。提前致谢。

导入 UIKit导入核心数据

ViewController 类:UIViewController、UITableViewDataSource、UITableViewDelegate {

var lists = [NSManagedObject]()
var deleteListIndexPath: NSIndexPath? = nil

@IBOutlet weak var myTableView: UITableView!

@IBAction func addItem(sender: AnyObject) {
    let alert = UIAlertController(title: "New List", message: "Add a new list", preferredStyle: .Alert)

    let saveAction = UIAlertAction(title: "Save", style: .Default) { (UIAlertAction) -> Void in

        let textField = alert.textFields![0] as UITextField
        if textField != "" {

          self.saveItem(textField.text!)
          self.myTableView.reloadData()
        }

       }


    let cancelAction = UIAlertAction(title: "Cancel", style: .Default, handler: nil)
    alert.addTextFieldWithConfigurationHandler(nil)
    alert.addAction(saveAction)
    alert.addAction(cancelAction)

    presentViewController(alert, animated: true, completion: nil)
}



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


func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
    let myCell:UITableViewCell = myTableView.dequeueReusableCellWithIdentifier("Prototype1")!

    let list = lists[indexPath.row]
    print(lists[indexPath.row])
    myCell.textLabel?.text = list.valueForKey("listTitle") as? String


    return myCell
}



override func viewDidLoad() {
    super.viewDidLoad()

   self.myTableView.dataSource = self
   self.myTableView.delegate = self

    let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let managedContext = appDelegate.managedObjectContext

    let fetchRequest = NSFetchRequest(entityName:"List")

    // you may need to sort the list
    let sortDescriptor1 = NSSortDescriptor(key: "listTitle", ascending: true)
    let sortDescriptors = [sortDescriptor1]
    fetchRequest.sortDescriptors = sortDescriptors

    var fetchedResults : [NSManagedObject] = []

    do
    {
        fetchedResults = try managedContext.executeFetchRequest(fetchRequest) as! [NSManagedObject]
    }
    catch
    {
        return
    }

    for list in fetchedResults
    {
        lists.append(list)
    }

    self.myTableView.reloadData()

}


func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
    return true
}

func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if(editingStyle == .Delete ) {
        // Find the LogItem object the user is trying to delete
        let logItemToDelete = lists[indexPath.row]
        let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
        let managedContext = appDelegate.managedObjectContext

        managedContext.deleteObject(logItemToDelete)
        self.myTableView.reloadData()


    }
}






func saveItem(Saveitem: String)
{
    let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate

    let managedContext = appDelegate.managedObjectContext

    let entity = NSEntityDescription.entityForName("List", inManagedObjectContext: managedContext)
    let item = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext)

    item.setValue(Saveitem, forKey: "listTitle")

    do {
        try managedContext.save()
        lists.append(item)


    }
    catch {
        print("Error")
    }
}

Answer 1

您可以使用 NSFetchedResultsController 类及其 NSFetchedResultsControllerDelegate 协议(protocol)方法。然后您可以非常轻松地更新、删除、插入或移动对象!

如果你的tableView没有更新？您可以使用 viewDidAppear 函数。