(Swift) Edit saved data at indexPathFOrSelectedRow using NSFetchedResultsController - ios

Question

I have a UITableViewController and a ordinary ViewController. In the VC (named nyTankning) there the user will type in info that is saved to a Core Data database. The database is loaded and displayed in the UITableVieController.
Now I want to be able to edit the info that is saved in the database. I have searched for the answer, but I haven´t found anything helpful, because I have used NSFetchedResultsController after following retrieving core data into tableview cells swift
Right now the code that I have wrote in the TableViewController looks like this:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
if segue.identifier == "update" {
let indexPath = self.tableView.indexPathForSelectedRow()
let selectedCell = fetchedResultsController?.indexPathForObject(indexPath!) as? NSManagedObject
let nyTankning: nyTankningViewController = segue.destinationViewController as nyTankningViewController
nyTankning.liter = selectedCell?.valueForKey("liter") as String
nyTankning.kronor = selectedCell?.valueForKey("kronor") as String
nyTankning.exisitingTankning = selectedCell
}
But I understand from the Debugger that the indexPath is not written properly.
2015-01-16 17:14:22.207 TankApp[4232:241135] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSIndexPath objectID]: unrecognized selector sent to instance 0x7c274660'
EDIT:Here is the full code for the whole UITableViewController:
import Foundation
import UIKit
import CoreData
class tankningarTableViewController: UITableViewController, NSFetchedResultsControllerDelegate {
var firstTime = 0
let managedObjectContext: NSManagedObjectContext? = (UIApplication.sharedApplication().delegate as? AppDelegate)?.managedObjectContext
var fetchedResultsController: NSFetchedResultsController?
override func viewDidLoad() {
super.viewDidLoad()
fetchedResultsController = NSFetchedResultsController(fetchRequest: allaTankningarFetchRequest(), managedObjectContext: managedObjectContext!, sectionNameKeyPath: nil, cacheName: nil)
fetchedResultsController?.delegate = self
fetchedResultsController?.performFetch(nil)
}
func alertViewFirstTime() {
let alertController = UIAlertController(title: "TankApp", message:
"Du kan lägga till en ny tankning genom att trycka på plusknappen (+).", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default,handler: nil))
self.presentViewController(alertController, animated: true, completion: nil)
}
func allaTankningarFetchRequest() -> NSFetchRequest {
var fetchRequest = NSFetchRequest(entityName: "Tankningslista")
let sortDescriptor = NSSortDescriptor(key: "datum", ascending: false)
fetchRequest.predicate = nil
fetchRequest.sortDescriptors = [sortDescriptor]
fetchRequest.fetchBatchSize = 20
return fetchRequest
}
override func viewDidAppear(animated: Bool) {
if firstTime == 0 {
alertViewFirstTime()
firstTime++
}
else {
return
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Potentially incomplete method implementation.
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete method implementation.
// Return the number of rows in the section.
return fetchedResultsController?.sections?[section].numberOfObjects ?? 0
}
//MARK: NSFetchedResultsController Delegate Functions
func controllerWillChangeContent(controller: NSFetchedResultsController) {
tableView.beginUpdates()
}
func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
switch type {
case NSFetchedResultsChangeType.Insert:
tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Delete:
tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Move:
break
case NSFetchedResultsChangeType.Update:
break
default:
break
}
}
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
}
switch editingStyle {
case .Delete:
managedObjectContext?.deleteObject(fetchedResultsController?.objectAtIndexPath(indexPath) as Model)
managedObjectContext?.save(nil)
case .Insert:
break
case .None:
break
}
}
func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
switch type {
case NSFetchedResultsChangeType.Insert:
tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Delete:
tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Move:
tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Update:
tableView.cellForRowAtIndexPath(indexPath!)
break
default:
break
}
}
func controllerDidChangeContent(controller: NSFetchedResultsController) {
tableView.endUpdates()
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Configure the cell...
let CellID: NSString = "Cell"
var cell: UITableViewCell = tableView.dequeueReusableCellWithIdentifier(CellID) as UITableViewCell
let fetchRequest = NSFetchRequest(entityName: "Tankningslista")
if let cellContact = fetchedResultsController?.objectAtIndexPath(indexPath) as? Model {
cell.textLabel?.text = "\(cellContact.datum)"
cell.detailTextLabel?.text = "\(cellContact.liter) Liter, \(cellContact.kronor) Kronor, \(cellContact.literpris) Kronor/Liter"
}
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.
return true
}
*/
/*
// 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
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
} else if editingStyle == .Insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
*/
/*
// Override to support rearranging the table view.
override func tableView(tableView: UITableView, moveRowAtIndexPath fromIndexPath: NSIndexPath, toIndexPath: NSIndexPath) {
}
*/
/*
// 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
}
*/
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
if segue.identifier == "update" {
let destination = segue.destinationViewController as nyTankningViewController
let indexPath = self.tableView.indexPathForCell(sender as Model)
destination.event = indexPath != nil ? fetchedResultsController.objectAtIndexPath(indexPath!) as? NSManagedObject : nil
}
}
}

Answer 1

I accomplish it like this using the ternary operator to handle the case for unwrapping the optional index path, but if let works just as well to avoid any crashes that may occur from that. Also, I would suggest using indexPathForCell and using sender as your cell rather than indexPathForSelectedRow.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
if segue.identifier == "SomeSegue" {
let destination = segue.destinationViewController as SomeViewController
let indexPath = self.tableView?.indexPathForCell(sender as SomeCell)
destination.event = indexPath != nil ? fetchedResultsController?.objectAtIndexPath(indexPath!) as? NSManagedObject : nil
}
}
With this method, you pass the entire managed object to the next view controller where you handle that accordingly. If you want to maintain setting all the destinations class variables from this method, you use if let to unwrap the optional index path like so:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
if segue.identifier == "SomeSegue" {
let destination = segue.destinationViewController as SomeViewController
if let indexPath = self.tableView?.indexPathForCell(sender as SomeCell) {
let object = fetchedResultsController?.objectAtIndexPath(indexPath) as? NSManagedObject
destination.foo = object?.bar
}
}
}
See a sample GitHub project here.