update CoreData Object not working correct

Question

I'm new to iOS development/CoreData and have searched for an answer to my specific problem, but haven't found one yet.

I have a TableView with some Objects from my database. Each of the objects has an attribute "name". If I open the details view of one of the objects and go back to the tableView with the "back" Button everything works fine. It also works if I do no changes to the "name" TextField and press the "done" Button to get back to my tableView. As soon as I do some changes in the "name" TextField I get this error:

Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (9) must be equal to the number of rows contained in that section before the update (9), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).

Why is there an object being deleted?

Here is the code of my DetailsStaticTableViewController.m:

#import "WeinStaticTableViewController.h"
#import "Wein.h"
#import "JSMToolBox.h"

@interface WeinStaticTableViewController ()

@end

@implementation WeinStaticTableViewController
@synthesize nameTextView;
@synthesize landTextView;
@synthesize herstellerTextView;
@synthesize wein = _wein;

- (id)initWithStyle:(UITableViewStyle)style
{
   self = [super initWithStyle:style];
   if (self) {
     // Custom initialization
   }
   return self;
}

- (void)viewDidLoad
{
   [super viewDidLoad];

   if (self.wein != nil) {
      self.nameTextView.text = self.wein.name;
   }
}

- (void) viewDidDisappear:(BOOL)animated
{
   [[JSMCoreDataHelper managedObjectContext] rollback];
   [super viewDidDisappear:animated];
}

- (void)didReceiveMemoryWarning
{
   [super didReceiveMemoryWarning];
   // Dispose of any resources that can be recreated.
   [self setNameTextView:nil];
   [self setLandTextView:nil];
   [self setHerstellerTextView:nil];
   self.wein = nil;
}

- (IBAction)barButtonItemDonePressed:(id)sender
{
   NSLog(@"%s", __PRETTY_FUNCTION__);
   if (self.wein != nil) {
       self.wein.name = self.nameTextView.text;
       [JSMCoreDataHelper saveManagedObjectContext:[JSMCoreDataHelper managedObjectContext]];
   }
   [self.navigationController popViewControllerAnimated:YES];
}
@end

Here is the code of my JSMCoreDataHelper.m:

#import "JSMCoreDataHelper.h"

@implementation JSMCoreDataHelper

+ (NSString*) directoryForDatabaseFilename
{
   return [NSHomeDirectory() stringByAppendingString:@"/Library/Private Documents"];
}

+ (NSString*) databaseFileName
{
   return @"database.sqlite";
}

+ (NSManagedObjectContext*) managedObjectContext
{
  static NSManagedObjectContext *managedObjectContext;
  if (managedObjectContext != nil) {
      return managedObjectContext;
  }

  NSError *error;
  // Verzeichnis unter dem das Datenbank-File abgespeichert werden soll, wird neu erzeugt, falls es noch nicht existiert.
  [[NSFileManager defaultManager] createDirectoryAtPath:[JSMCoreDataHelper directoryForDatabaseFilename] withIntermediateDirectories:YES attributes:nil error:&error];

  if (error) {
      NSLog(@"Fehler: %@", error.localizedDescription);
      return nil;
  }

  NSString *path = [NSString stringWithFormat:@"%@/%@", [JSMCoreDataHelper directoryForDatabaseFilename], [JSMCoreDataHelper databaseFileName]];
  NSURL *url = [NSURL fileURLWithPath:path];

  NSManagedObjectModel *managedModel = [NSManagedObjectModel mergedModelFromBundles:nil];

  NSPersistentStoreCoordinator *storeCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedModel];

  if (! [storeCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error]) {
      NSLog(@"Fehler: %@", error.localizedDescription);
      return nil;
  }

  managedObjectContext = [[NSManagedObjectContext alloc] init];
  managedObjectContext.persistentStoreCoordinator = storeCoordinator;

  return managedObjectContext;
}

+ (id) insertManagedObjectOfClass: (Class) aClass inManagedObjectContext: (NSManagedObjectContext*) managedObjectContext
{
   NSManagedObject *managedObject = [NSEntityDescription insertNewObjectForEntityForName:NSStringFromClass(aClass) inManagedObjectContext:managedObjectContext];
   return managedObject;
}

+ (BOOL) saveManagedObjectContext: (NSManagedObjectContext*) managedObjectContext
{
   NSError *error;
   if (! [managedObjectContext save:&error]) {
       NSLog(@"Fehler: %@", error.localizedDescription);
       return NO;
   }
   return YES;
}

+ (NSArray*) fetchEntitiesForClass: (Class) aClass withPredicate: (NSPredicate*) predicate inManagedObjectContext: (NSManagedObjectContext*) managedObjectContext
{
   NSError *error;
   NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
   NSEntityDescription *entityDescription = [NSEntityDescription entityForName:NSStringFromClass(aClass) inManagedObjectContext:managedObjectContext];
   fetchRequest.entity = entityDescription;
   fetchRequest.predicate = predicate;

   NSArray *items = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
   if (error) {
       NSLog(@"Fehler: %@", error.localizedDescription);
       return nil;
   }
   return items;
}

+ (BOOL) performFetchOnFetchedResultsController: (NSFetchedResultsController*) fetchedResultsController
{
   NSError *error;
   if (! [fetchedResultsController performFetch:&error]) {
       NSLog(@"Fehler: %@", error.localizedDescription);
       return NO;
   }
   return YES;
}

@end

And finally the numberOfSections and numberOfRowsInSection of my MainTableViewController:

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
   // Return the number of sections.
   return [[self.fetchedResultsController sections] count];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
   // Return the number of rows in the section.
   return [[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects];
}

Any clue could help...thank you !

Answer 1

Heres my code using a NSFetchedResultsController, this works fine with your code for managing CoreData.

Hope this helps.

#import "Person.h"
#import "mainViewController.h"
#import "JSMCoreDataHelper.h"
#import "staticInfoViewController.h"

@implementation mainViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Load From CoreData
    NSError *error;
    if (![[self fetchedResultsController] performFetch:&error]) {
        // Update to handle the error appropriately.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        exit(-1);  // Fail
    }
}

#pragma mark - TableView DataSource

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return [[self.fetchedResultsController sections] count];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return [[[self.fetchedResultsController sections] objectAtIndex:section] numberOfObjects];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }

    [self configureCell:cell atIndexPath:indexPath];

    return cell;
}

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
    Person *p = [_fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = [NSString stringWithFormat:@"Name: %@", p.name];
}

#pragma mark - TableView Delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    staticInfoViewController *info = [[staticInfoViewController alloc] initWithNibName:@"staticInfoViewController" bundle:[NSBundle mainBundle]];
    info.currentPerson = [_fetchedResultsController objectAtIndexPath:indexPath];
    [self.navigationController pushViewController:info animated:YES];
}

#pragma mark - Set NSFetchedResultsController

- (NSFetchedResultsController *)fetchedResultsController {

    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription
                                   entityForName:@"Person" inManagedObjectContext:[JSMCoreDataHelper managedObjectContext]];
    [fetchRequest setEntity:entity];

    NSSortDescriptor *sort = [[NSSortDescriptor alloc]
                              initWithKey:@"name" ascending:YES];
    [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

    [fetchRequest setFetchBatchSize:20];

    NSFetchedResultsController *theFetchedResultsController =
    [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                        managedObjectContext:[JSMCoreDataHelper managedObjectContext] sectionNameKeyPath:nil
                                                   cacheName:@"cache"];
    self.fetchedResultsController = theFetchedResultsController;
    _fetchedResultsController.delegate = self;

    return _fetchedResultsController;
}

#pragma mark - NSFetchedResultsController Delegate

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    // The fetch controller is about to start sending change notifications, so prepare the table view for updates.
    [self.tableView beginUpdates];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {

    UITableView *tableView = self.tableView;

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray
                                               arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:[NSArray
                                               arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id )sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    // The fetch controller has sent all current change notifications, so tell the table view to process all updates.
    [self.tableView endUpdates];
}

@end

Answer 2

you have wrong number of data in UI and in core data. the row count dosnt match in UI and core data. you have daleted one row but UI/fetchresultcontroller does not know about and tries to read it from the database. either refetch after changes or implement the fetch result controller delegate:

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath;

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type;

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller;

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller;

do not forget to set fetch result controller to self.( viel spass )