Can't delete a record from core data - ios

Question

i have a table view where Im performing a deletion: (just the relevant methods)
#import "StackTableViewController.h"
#import "Target.h"
#import "StackTableViewCell.h"
#import "HomeViewController.h"
#import "CoreDataStack.h"
#interface StackTableViewController () <NSFetchedResultsControllerDelegate>
#property (nonatomic, strong) NSFetchedResultsController *fetchedResultController;
#end
#implementation StackTableViewController
- (id)init {
self = [super initWithNibName:#"StackTableViewController" bundle:nil];
if (self) {
// Do something
[self.fetchedResultController performFetch:nil];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
Target *current = [self.fetchedResultController objectAtIndexPath:indexPath];
self.currentTarget = current.body;
}
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
self.navigationItem.rightBarButtonItem = self.editButtonItem;
[self.fetchedResultController performFetch:nil];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
Target *current = [self.fetchedResultController objectAtIndexPath:indexPath];
self.currentTarget = current.body;
}
- (void)viewWillLayoutSubviews {
[self.navigationController setNavigationBarHidden:NO animated:YES];
}
- (void)viewWillDisappear:(BOOL)animated {
[self.navigationController setNavigationBarHidden:YES animated:YES];
}
// just to ignor a warning
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 44;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
// Return the number of sections.
return self.fetchedResultController.sections.count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
id <NSFetchedResultsSectionInfo> sectionInfo = [self.fetchedResultController sections][section];
return [sectionInfo numberOfObjects];
}
- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath
{
return UITableViewCellEditingStyleDelete;
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
Target *target = [self.fetchedResultController objectAtIndexPath:indexPath];
CoreDataStack *stack = [CoreDataStack defaultStack];
[[stack managedObjectContext] deleteObject:target];
[stack saveContext];
if ([_delegate respondsToSelector:#selector(didDeleteObject)]) {
[_delegate didDeleteObject];
}
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *cellIdentifier = #"StackTableViewCell";
Target *target = [self.fetchedResultController objectAtIndexPath:indexPath];
StackTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (!cell)
{
NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:#"StackTableViewCell" owner:self options:nil];
cell = [topLevelObjects objectAtIndex:0];
}
cell.cellLabel.text = target.body;
cell.cellLabel.font = [UIFont fontWithName:#"Candara-Bold" size:20];
// Configure the cell...
return cell;
}
- (NSFetchRequest *)targetsFetchRequest {
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:#"Target"];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"time" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
return fetchRequest;
}
- (NSFetchedResultsController *)fetchedResultController {
if (_fetchedResultController != nil) {
return _fetchedResultController;
}
CoreDataStack *stack = [CoreDataStack defaultStack];
NSFetchRequest *fetchRequest = [self targetsFetchRequest];
_fetchedResultController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:stack.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
_fetchedResultController.delegate = self;
return _fetchedResultController;
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id<NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch (type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationAutomatic];
default:
break;
}
}
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
switch (type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertRowsAtIndexPaths:#[newIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeUpdate:
[self.tableView reloadRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
default:
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
and as you can see i created a delegate method for the table view controller to tell the home view controller that a deletion was made, so I can update some table in the home view controller.
HomeViewController.h: (just the relevant methods)
#import "HomeViewController.h"
#import "CreateViewController.h"
#import "ProfileViewController.h"
#import "StackTableViewController.h"
#interface HomeViewController () <StackTableViewControllerDelegate>
#property (strong, nonatomic) IBOutlet UILabel *homeLabel;
#end
#implementation HomeViewController
- (id)init {
self = [super initWithNibName:#"HomeViewController" bundle:nil];
if (self) {
// Do something
stackTableViewController = [[StackTableViewController alloc] init];
stackTableViewController.delegate = self;
}
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
[self.navigationController setNavigationBarHidden:YES];
self.homeLabel.font = [UIFont fontWithName:#"Candara-Bold" size:40];
self.homeLabel.text = stackTableViewController.currentTarget;
}
- (void)didDeleteObject {
self.homeLabel.text = stackTableViewController.currentTarget;
}
but now not only that the label is not getting updated whenever the first cell was deleted, I can't perform the deletion....it seems to crash at the saveContext call...
this is the error i'm getting:
CoreData: error: Serious application error. Exception was caught during Core Data change processing. This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification. *** -[NSArray indexOfObject:inRange:]: range {0, 4} extends beyond bounds [0 .. 2] with userInfo (null)
2014-12-21 15:35:18.392 Treats[4153:582136] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSArray indexOfObject:inRange:]: range {0, 4} extends beyond bounds [0 .. 2]'
this is my CoreDataStack class (singleton):
#import "CoreDataStack.h"
#implementation CoreDataStack
#pragma mark - Core Data stack
#synthesize managedObjectContext = _managedObjectContext;
#synthesize managedObjectModel = _managedObjectModel;
#synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
+ (instancetype)defaultStack {
static CoreDataStack *defaultStack;
static dispatch_once_t onceTocken;
dispatch_once (&onceTocken, ^{
defaultStack = [[self alloc] init];
});
return defaultStack;
}
- (NSURL *)applicationDocumentsDirectory {
// The directory the application uses to store the Core Data store file. This code uses a directory named "digitalCrown.Treats" in the application's documents directory.
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
- (NSManagedObjectModel *)managedObjectModel {
// The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
if (_managedObjectModel != nil) {
return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:#"Treats" withExtension:#"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
// Create the coordinator and store
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:#"Treats.sqlite"];
NSError *error = nil;
NSString *failureReason = #"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
// Report any error we got.
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
dict[NSLocalizedDescriptionKey] = #"Failed to initialize the application's saved data";
dict[NSLocalizedFailureReasonErrorKey] = failureReason;
dict[NSUnderlyingErrorKey] = error;
error = [NSError errorWithDomain:#"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return _persistentStoreCoordinator;
}
- (NSManagedObjectContext *)managedObjectContext {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (!coordinator) {
return nil;
}
_managedObjectContext = [[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
return _managedObjectContext;
}
#pragma mark - Core Data Saving support
- (void)saveContext {
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
NSError *error = nil;
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
}
#end
please help :/
tnx

Answer 1

The error you received can be caused by accessing the Persistent Store Coordinator from two threads simultaneously.
As we've figured out throughout the comment thread, in this particular case, the error was caused because the core data fetch was performed in two places simultaneously upon the view controller's creation by having this line
[self.fetchedResultController performFetch:nil];
in both the init and viewDidLoad methods. So to solve this problem, only call performFetch in either init or viewDidLoad -- not both.