tableView.reloadData() causing a crash of the app - swift

Question

In the Swift app, I present an addition view to add an element to the CoreData database. If I call tableview.reloadData(), the app crashes on the + button on the main screen. If I omit the reload data then the add view is presented and the data is added to the CoreData file.
the main view, from configureCell down:
func configureCell(cell: TransectTableViewCell, indexPath:NSIndexPath) {
let transectEntry = fetchedResultController.objectAtIndexPath(indexPath) as! Transects
cell.transectNameLabel.text = transectEntry.transectName
cell.transectNameLabel.textColor = UIColor.blackColor()
cell.transectNameLabel.shadowColor = UIColor.whiteColor()
cell.transectNameLabel.shadowOffset = CGSizeMake(1, 1)
}
func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
let countEntry = fetchedResultController.objectAtIndexPath(indexPath) as! Transects
coreDataStack.context.deleteObject(countEntry)
coreDataStack.saveContext()
}
}
func tableView(tableView: UITableView,
heightForRowAtIndexPath indexPath: NSIndexPath)
-> CGFloat {
return 50;
}
func didFinishViewController(viewController: AddTransectViewController, didSave: Bool) {
if didSave {
var error: NSError? = nil
let context = viewController.context
self.coreDataStack.saveContext()
}
dismissViewControllerAnimated(true, completion: {})
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "addTransectSegue" {
let newTransectViewController = segue.destinationViewController as! AddTransectViewController
let transectEntryEntity = NSEntityDescription.entityForName("Transects", inManagedObjectContext: coreDataStack.context)
let newTransectEntry = Transects(entity: transectEntryEntity!, insertIntoManagedObjectContext: coreDataStack.context)
newTransectViewController.transectNewEntry = newTransectEntry
newTransectViewController.context = newTransectEntry.managedObjectContext
newTransectViewController.delegate = self
}
if segue.identifier == "transectTasksSegue" {
let indexPath = tableView.indexPathForSelectedRow()!
let transectSelected = fetchedResultController.objectAtIndexPath(indexPath) as! Transects
let tasksViewController = segue.destinationViewController as! TransectTasksViewController
tasksViewController.coreDataStack = coreDataStack
tasksViewController.selectedTransect = transectSelected
}
}
func controllerDidChangeContent(controller:
NSFetchedResultsController) {
tableView.reloadData()
}
The addition view is:
import UIKit
import CoreData
import Foundation
protocol TransectDelegate {
func didFinishViewController(ViewController:AddTransectViewController, didSave:Bool)
}
class AddTransectViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var transectNameTextField: UITextField!
#IBOutlet weak var latitudeTextField: UITextField!
#IBOutlet weak var longitudeTextField: UITextField!
#IBOutlet weak var altitudeTextField: UITextField!
var transectNewEntry: Transects!
var context: NSManagedObjectContext!
var delegate:TransectDelegate?
override func viewDidLoad() {
super.viewDidLoad()
}
override func prefersStatusBarHidden() -> Bool {
return true
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func updateTransectEntry() {
if let entry = transectNewEntry {
entry.transectName = transectNameTextField.text
entry.latitude = latitudeTextField.text
entry.longitude = longitudeTextField.text
entry.altitude = altitudeTextField.text
}
}
#IBAction func cancelButtonWasTapped(sender: AnyObject) {
delegate?.didFinishViewController(self, didSave: false)
}
#IBAction func saveButtonWasTapped(sender: AnyObject) {
updateTransectEntry()
delegate?.didFinishViewController(self, didSave: true)
}
}
I am missing something, but cannot see what. Ideas would be welcome.
The app hangs up on cell.transectNameLabel.text = transectEntry.transectName
with: Thread 1:EXC_BAD_ACCESS (code=1, address=0x0)
My real confusion is that this works perfectly:
import UIKit
import CoreData
class PlantSpeciesViewController: UIViewController, NSFetchedResultsControllerDelegate, PlantSpeciesDelegate, UITableViewDataSource, UITableViewDelegate {
#IBOutlet var tableView:UITableView!
var coreDataStack: CoreDataStack!
lazy var fetchedResultController:
NSFetchedResultsController = self.plantSpeciesFetchedResultsController()
var plantSpecies: PlantSpecies!
var selectedFamily: PlantFamily!
var context: NSManagedObjectContext!
var plantFamilyName: String!
override func viewDidLoad() {
super.viewDidLoad()
tableView.backgroundColor = UIColor.clearColor()
view.backgroundColor = UIColor(patternImage: UIImage (named: "Monitor backdrop.png")!)
self.title = plantFamilyName
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func plantSpeciesFetchedResultsController()
->NSFetchedResultsController {
fetchedResultController =
NSFetchedResultsController(
fetchRequest: plantSpeciesFetchRequest(),
managedObjectContext: coreDataStack.context,
sectionNameKeyPath: nil,
cacheName: nil)
fetchedResultController.delegate = self
var error: NSError? = nil
if (!fetchedResultController.performFetch(&error)){
println("Error: \(error?.localizedDescription)")
abort()
}
return fetchedResultController
}
func plantSpeciesFetchRequest() -> NSFetchRequest {
let fetchRequest = NSFetchRequest(entityName: "PlantSpecies")
fetchRequest.fetchBatchSize = 20
let predicate = NSPredicate(format: "familyName == %#", selectedFamily)
fetchRequest.predicate = predicate
let sortDescriptor = NSSortDescriptor(key: "plantSpecies", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
//var error: NSError?
return fetchRequest
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return fetchedResultController.sections!.count
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return fetchedResultController.sections![section].numberOfObjects
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("plantSpeciesCell", forIndexPath: indexPath) as! PlantSpeciesTableViewCell
cell.backgroundColor = UIColor.clearColor()
configureCell(cell, indexPath: indexPath)
return cell
}
func configureCell(cell: PlantSpeciesTableViewCell, indexPath:NSIndexPath) {
let plantEntry = fetchedResultController.objectAtIndexPath(indexPath) as! PlantSpecies
cell.speciesNameLabel.text = plantEntry.plantSpecies
cell.speciesNameLabel.textColor = UIColor.blackColor()
cell.speciesNameLabel.shadowColor = UIColor.whiteColor()
cell.speciesNameLabel.shadowOffset = CGSizeMake(1, 1)
cell.speciesImageView.image = UIImage (data: plantEntry.plantImage)
}
func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
let countEntry = fetchedResultController.objectAtIndexPath(indexPath) as! PlantFamily
coreDataStack.context.deleteObject(countEntry)
coreDataStack.saveContext()
}
}
func tableView(tableView: UITableView,
heightForRowAtIndexPath indexPath: NSIndexPath)
-> CGFloat {
return 90;
}
func didFinishViewController(viewController: AddPlantSpeciesViewController, didSave: Bool) {
if didSave {
var error: NSError? = nil
let context = viewController.context
self.coreDataStack.saveContext()
}
dismissViewControllerAnimated(true, completion: {})
}
// MARK: - Navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "addSpeciesSegue" {
let newPlantViewController = segue.destinationViewController as! AddPlantSpeciesViewController
let plantEntryEntity = NSEntityDescription.entityForName("PlantSpecies", inManagedObjectContext: coreDataStack.context)
let newSpeciesEntry = PlantSpecies(entity: plantEntryEntity!, insertIntoManagedObjectContext: coreDataStack.context)
newPlantViewController.selectedFamily = selectedFamily
newPlantViewController.plantNameEntry = newSpeciesEntry
newPlantViewController.context = newSpeciesEntry.managedObjectContext
newPlantViewController.delegate = self
}
}
func controllerDidChangeContent(controller:
NSFetchedResultsController) {
tableView.reloadData()
}
}
coupled with:
import UIKit
import CoreData
import Foundation
protocol PlantSpeciesDelegate {
func didFinishViewController(ViewController:AddPlantSpeciesViewController, didSave:Bool)
}
class AddPlantSpeciesViewController: UIViewController, UITextFieldDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
#IBOutlet weak var plantNameTextField: UITextField!
#IBOutlet weak var plantImageView: UIImageView!
#IBOutlet weak var imageSwitch: UISwitch!
#IBOutlet weak var imageFromFileButton: UIButton!
#IBOutlet weak var imageFromCameraButton: UIButton!
let imagePicker = UIImagePickerController()
var plantNameEntry: PlantSpecies!
var selectedFamily: PlantFamily!
var passedPlantFamily: String!
var newPlantName: String!
var newImageData: NSData!
var context: NSManagedObjectContext!
var delegate:PlantSpeciesDelegate?
override func viewDidLoad() {
super.viewDidLoad()
plantImageView.image = UIImage(named: "placeholder image.jpg")
imagePicker.delegate = self
}
override func prefersStatusBarHidden() -> Bool {
return true
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func imageSourceSwitch(sender: AnyObject) {
if imageSwitch.on == true
{
self.imageFromFileButton.enabled = true
self.imageFromCameraButton.enabled = false
}
else
{
self.imageFromCameraButton.enabled = true
self.imageFromFileButton.enabled = false
}
}
#IBAction func imageFromFile(sender: AnyObject) {
imagePicker.sourceType = .PhotoLibrary
presentViewController(imagePicker, animated: true, completion: nil)
}
#IBAction func imageFromCamera(sender: AnyObject) {
imagePicker.sourceType = .Camera
presentViewController(imagePicker, animated: true, completion: nil)
}
func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) {
self.plantImageView.image = image
dismissViewControllerAnimated(true, completion: nil)
}
#IBAction func getPlantName() {
newPlantName = plantNameTextField.text
plantNameTextField.resignFirstResponder()
}
func updateSpeciesEntry() {
if let entry = plantNameEntry {
entry.plantSpecies = newPlantName
entry.plantImage = UIImageJPEGRepresentation(plantImageView.image, 1.0)
entry.familyName = selectedFamily
}
}
#IBAction func cancelButtonWasTapped(sender: AnyObject) {
delegate?.didFinishViewController(self, didSave: false)
}
#IBAction func saveButtonWasTapped(sender: AnyObject) {
updateSpeciesEntry()
delegate?.didFinishViewController(self, didSave: true)
}
}
So, what is the difference?

Answer 1

This happen to me too, fixed it with:
dispatch_async(dispatch_get_main_queue(), ^{
[self.tableView reloadData];
});
instead of just tableView.reloadData()
, cause it seems that it was being called from wrong thread.

Answer 2

The reason for the crash is most likely that the table cannot load the data, for example a value does not exist and is being force unwrapped. The crash only happens, therefore, when you try to collect the data. Check through all the values to be sure.

Answer 3

I'd like to expand on GJZ answer & what brought me here. I have UITableViewCells that have a textfield. I attempted to get values the user entered from the field.
let companyNameCell: TextEntryCell = self.tableView.cellForRow(at: IndexPath(row: 0, section: 0)) as! TextEntryCell
what I realized is that when I dynamically hide and showed rows by changing the cell heights using the tableview.reloadrows method, the app would crash if it attempted to read a cell the user could not see on their screen. that is because the cells I think were deallocated.