Issue deleting a row using NSFetchedResultController in swift 2.1 - ios

Question

Hi guys I am using NSFetchedResultController but I am getting issues when I delete a record (even with the first record).
Here is the code of my View Controller :
import UIKit
import CoreData
class FoldersListViewController: UITableViewController, NSFetchedResultsControllerDelegate {
#IBOutlet var myFoldersTableView: UITableView!
// public property that represent the current selected row in a tableview; this will be use in the shouldPerformSegueWithIdentifier
// function because the method doesn't have a parameter for the index path of the selected row.
var selectedRowIndex: NSIndexPath? = nil
//Public property that will be controlling all the manipulation of CoreData.
var fetchedResultController: NSFetchedResultsController!
override func viewDidLoad() {
super.viewDidLoad()
let config = Settings()
config.ReadConfiguration()
// Uncomment the following line to preserve selection between presentations
// self.clearsSelectionOnViewWillAppear = false
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
//self.navigationItem.rightBarButtonItem = self.editButtonItem()
self.loadFolders()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Potentially incomplete method implementation.
// Return the number of sections.
return fetchedResultController.sections!.count
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete method implementation.
// Return the number of rows in the section.
let sectionInfo = fetchedResultController.sections![section]
return sectionInfo.numberOfObjects
}
func configureCell(cell: cellFolder,indexPath: NSIndexPath)
{
let folder = fetchedResultController.objectAtIndexPath(indexPath) as! Folder
if(folder.picture.length > 0){
let newSize:CGSize = CGSize(width: 64,height: 64)
let rect = CGRectMake(0,0, newSize.width, newSize.height)
UIGraphicsBeginImageContextWithOptions(newSize, true, 0.0)
let photo = UIImage(data: folder.picture)
UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
photo!.drawInRect(rect)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
cell.imageView?.contentMode = UIViewContentMode.ScaleAspectFill
cell.imageView?.layer.masksToBounds = true
cell.imageView?.layer.cornerRadius = 15.0
cell.imageView?.clipsToBounds = true
cell.imageView?.image = newImage
}
cell.labelFolderName.text = folder.name
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell: cellFolder = tableView.dequeueReusableCellWithIdentifier("cellFolder", forIndexPath: indexPath) as! cellFolder
self.configureCell(cell, indexPath: indexPath)
return cell
}
// Override to support conditional editing of the table view.
override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return NO if you do not want the specified item to be editable.
if (tableView.editing){
return false
}
else
{
return true
}
}
func loadFolders() {
let request = NSFetchRequest(entityName: "Folder")
let handler = HACoreDataHandler()
let sortDescriptor = NSSortDescriptor(key: "name",ascending: true)
request.sortDescriptors = [sortDescriptor]
fetchedResultController = NSFetchedResultsController(fetchRequest: request, managedObjectContext: handler.context!, sectionNameKeyPath: nil, cacheName: nil)
fetchedResultController.delegate = self
do
{
try fetchedResultController.performFetch()
} catch let error as NSError {
let alert = UIAlertController(title: "Error", message: error.description, preferredStyle: UIAlertControllerStyle.Alert)
let dismiss = UIAlertAction(title: "Dismiss", style: .Default) { (alertAction: UIAlertAction) ->
Void in
}
alert.addAction(dismiss)
presentViewController(alert, animated: true, completion: nil)
}
}
func controllerWillChangeContent(controller: NSFetchedResultsController) {
tableView.beginUpdates()
}
func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType)
{
let indexSet = NSIndexSet(index:sectionIndex)
switch type {
case .Insert:
myFoldersTableView.insertSections(indexSet, withRowAnimation: .Automatic)
case .Delete:
myFoldersTableView.deleteSections(indexSet, withRowAnimation: .Automatic)
default:
break
}
}
func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?)
{
switch type{
case .Insert:
myFoldersTableView.insertRowsAtIndexPaths([newIndexPath!], withRowAnimation: .Automatic)
case .Delete:
myFoldersTableView.deleteRowsAtIndexPaths([indexPath!], withRowAnimation: .Automatic)
case .Update:
myFoldersTableView.reloadRowsAtIndexPaths([indexPath!], withRowAnimation: .Automatic)
case .Move:
if (indexPath != newIndexPath){
myFoldersTableView.deleteRowsAtIndexPaths([indexPath!], withRowAnimation: .Automatic)
myFoldersTableView.insertRowsAtIndexPaths([newIndexPath!], withRowAnimation: .Automatic)
}
}
}
func controllerDidChangeContent(controller: NSFetchedResultsController) {
myFoldersTableView.endUpdates()
}
override func viewWillAppear(animated: Bool) {
self.loadFolders()
myFoldersTableView.reloadData()
}
// Override to support editing the table view.
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
// Delete the row from the data source
let item = self.fetchedResultController.objectAtIndexPath(indexPath) as! Folder
let handler = HACoreDataHandler()
handler.context?.deleteObject(item)
var error: NSError?
do {
try handler.context?.save()
} catch let error1 as NSError {
error = error1
}
if(error != nil){
let alert = UIAlertController(title: "Error", message: error?.description, preferredStyle: UIAlertControllerStyle.Alert)
let dismiss = UIAlertAction(title: "Dismiss", style: .Default) { (alertAction: UIAlertAction) ->
Void in
}
alert.addAction(dismiss)
presentViewController(alert, animated: true, completion: nil)
}
self.myFoldersTableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
}
}
override func tableView(tableView: UITableView, editActionsForRowAtIndexPath indexPath: NSIndexPath) -> [UITableViewRowAction]? {
let delete = UITableViewRowAction(style: .Default, title: "Delete") { (action:UITableViewRowAction, indexPath:NSIndexPath) -> Void in
self.selectedRowIndex = indexPath
let folder = self.fetchedResultController.objectAtIndexPath(indexPath) as! Folder
let handler = HACoreDataHandler()
handler.context?.deleteObject(folder)
do {
try handler.context?.save()
} catch let error as NSError {
let alert = UIAlertController(title: "Error", message: error.description, preferredStyle: UIAlertControllerStyle.Alert)
let dismiss = UIAlertAction(title: "Dismiss", style: .Default) { (alertAction: UIAlertAction) ->
Void in
}
alert.addAction(dismiss)
self.presentViewController(alert, animated: true, completion: nil)
}
self.myFoldersTableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Fade)
}
delete.backgroundColor = UIColor.redColor()
let details = UITableViewRowAction(style: .Normal, title: "Edit") { (action: UITableViewRowAction, indexPath: NSIndexPath) -> Void in
let tmpFolder = self.fetchedResultController.objectAtIndexPath(indexPath) as! Folder
let destination = self.storyboard?.instantiateViewControllerWithIdentifier("editFolder") as! EditFolderViewController
destination.folder = tmpFolder
let navigationController = self.parentViewController as! UINavigationController
var response: Bool = true
if( tmpFolder.isprotected == true){
let alert = UIAlertController(title: "Password Validation", message: "Please enter the folder password", preferredStyle: .Alert)
//2. Add the text field. You can configure it however you need.
alert.addTextFieldWithConfigurationHandler({ (textField) -> Void in
textField.text = ""
})
alert.addAction(UIAlertAction(title: "Login", style: .Default, handler: { (action) -> Void in
let textField = alert.textFields![0]
if (tmpFolder.password == textField.text){
response = true
} else {
let wrongPasswordAlert = UIAlertController(title: "Error", message: "Invalid password.", preferredStyle: UIAlertControllerStyle.Alert)
let dismiss = UIAlertAction(title: "Dismiss", style: .Default) { (alertAction: UIAlertAction) ->
Void in
}
wrongPasswordAlert.addAction(dismiss)
self.presentViewController(wrongPasswordAlert, animated: true, completion: nil)
response = false
} // else if (folder.password == textField.text)
}))
// 4. Present the alert.
self.presentViewController(alert, animated: true, completion: nil)
}
// 4. Present the alert.
if(response){
navigationController.pushViewController(destination, animated: true)
}
//navigationController.presentViewController(destination, animated: true, completion: nil)
//self.showDetailViewController(destination, sender: self)
}
details.backgroundColor = UIColor.grayColor()
return [delete,details]
}
// Override to support rearranging the table view.
//override func tableView(tableView: UITableView, moveRowAtIndexPath fromIndexPath: NSIndexPath, toIndexPath: NSIndexPath) {
//
//}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
myFoldersTableView.reloadData()
}
// Override to support conditional rearranging of the table view.
override func tableView(tableView: UITableView, canMoveRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return NO if you do not want the item to be re-orderable.
return true
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier=="listOcassions"){
let ocassions = segue.destinationViewController as! DatesViewController
let folder = fetchedResultController.objectAtIndexPath(self.selectedRowIndex!) as! Folder
ocassions.folder = folder
}
}
override func shouldPerformSegueWithIdentifier(identifier: String, sender: AnyObject?) -> Bool {
var response: Bool = true
if identifier == "listOcassions" {
self.selectedRowIndex = myFoldersTableView.indexPathForSelectedRow
let folder = fetchedResultController.objectAtIndexPath(self.selectedRowIndex!) as! Folder
if( folder.isprotected == true){
let alert = UIAlertController(title: "Password Validation", message: "Please enter the folder password", preferredStyle: .Alert)
//2. Add the text field. You can configure it however you need.
alert.addTextFieldWithConfigurationHandler({ (textField) -> Void in
textField.text = ""
})
alert.addAction(UIAlertAction(title: "Login", style: .Default, handler: { (action) -> Void in
let textField = alert.textFields![0]
if (folder.password == textField.text){
response = true
self.performSegueWithIdentifier("listOcassions", sender: self)
} else {
let wrongPasswordAlert = UIAlertController(title: "Error", message: "Invalid password.", preferredStyle: UIAlertControllerStyle.Alert)
let dismiss = UIAlertAction(title: "Dismiss", style: .Default) { (alertAction: UIAlertAction) ->
Void in
}
wrongPasswordAlert.addAction(dismiss)
self.presentViewController(wrongPasswordAlert, animated: true, completion: nil)
response = false
} // else if (folder.password == textField.text)
}))
// 4. Present the alert.
self.presentViewController(alert, animated: true, completion: nil)
} //if folder.isprotected == true
}
return response
}
}
I can add records but when I try to delete the record I get the following error message:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'attempt to delete row 0 from section 0 which only contains 0 rows before the update'
I know there are similar questions like this before but none of the answers for those questions (that i have applied and some of them are in the copied code) did not solve my issue.
Thanks a lot in advance.
Julio.

Answer 1

The deleteObject in your commitEditingStyle: method triggers the FRC delegate methods, which then delete the relevant row from the table view. So you can delete this line:
self.myFoldersTableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
from the commitEditingStyle method - it is effectively deleting the same row twice. Hence the error.
Likewise for editActionsForRowAtIndexPath.