Core data objects update through loop

Question

I have a tableView showing core-data objects. On the same view there are five buttons. Each button action should update the value of an attribute from the objects. As an example, I will show you what I have to update the attribute 'isDone':

- (IBAction)allDoneAction:(id)sender {

    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
    int i=0;
    for (NSManagedObject *mo in context)
    {
        [mo setValue:@"Done" forKey:@"isDone"];i++;
    }

    [managedObjectContext save:nil];

}

This method throws following following exception:

NSManagedObjectContext countByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x9a6b0a0
2014-01-06 19:01:43.862 To-Do Pro[679:a0b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSManagedObjectContext countByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x9a6b0a0'

What do I need to avoid the exception and obtain the desired update? Here is my NSFetchedResultsController:

- (NSFetchedResultsController *)fetchedResultsController
{
  if (fetchedResultsController) return fetchedResultsController;

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

  [fetchRequest setEntity:entity];

  NSSortDescriptor *sortDescriptor = 
              [[NSSortDescriptor alloc] initWithKey:@"displayOrder" 
                                          ascending:YES];

  NSArray *sortDescriptors = [[NSArray alloc] 
                              initWithObjects:sortDescriptor, nil];
    //SOLO TO-DOS DE TODAY


    todayDate = [NSDate date];

    NSCalendar* calendar = [NSCalendar currentCalendar];
    NSDateComponents* components = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit fromDate:todayDate]; // Get necessary date components




    NSNumber *yearBuscado = [NSNumber numberWithLong:[components year]];
    NSNumber *mesBuscado = [NSNumber numberWithLong:[components month]];
    NSNumber *diaBuscado = [NSNumber numberWithLong:[components day]];

   // NSString *tipourgente = @"Urgent";
   // NSString *tipocolor = @"Yellow";

    NSString *textoNotDone = @"Not done";
    NSString *textoNotDeleted = @"Not deleted";

    NSPredicate *yearPredicate = [NSPredicate predicateWithFormat:@"todoYear == %@", yearBuscado];
    NSPredicate *monthPredicate = [NSPredicate predicateWithFormat:@"todoMonth == %@", mesBuscado];
    NSPredicate *dayPredicate = [NSPredicate predicateWithFormat:@"todoDay == %@", diaBuscado];
    NSPredicate *notDonePredicate = [NSPredicate predicateWithFormat:@"isDone== %@", textoNotDone];
    NSPredicate *notDeletedPredicate = [NSPredicate predicateWithFormat:@"isSemiDeleted==%@", textoNotDeleted];
    // NSPredicate *urgentPredicate = [NSPredicate predicateWithFormat:@"urgent == %@", tipourgente];
   // NSPredicate *colorPredicate = [NSPredicate predicateWithFormat:@"color == %@", tipocolor];

  [fetchRequest setSortDescriptors:sortDescriptors];






  NSPredicate *busqueda = [NSCompoundPredicate andPredicateWithSubpredicates:@[yearPredicate,monthPredicate,dayPredicate,notDonePredicate,notDeletedPredicate]];

    [fetchRequest setPredicate:busqueda];
  NSFetchedResultsController *aFetchedResultsController =
              [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                                                  managedObjectContext:managedObjectContext
                                                    sectionNameKeyPath:nil cacheName:nil];
  aFetchedResultsController.delegate = self;
  [self setFetchedResultsController:aFetchedResultsController];


  [aFetchedResultsController release];
  [fetchRequest release];
  [sortDescriptor release];
  [sortDescriptors release];


  return fetchedResultsController;
}

Community · Accepted Answer · 2017-05-23 12:19:10Z

3

Ok, I know absolutely nothing about core data, but from what I have researched in the last two minutes it appears as though you do not loop over An object of NSManagedObjectContext. You need to create a search within the context and get the results from that. Then iterate through the results and modify willy nilly.

Here is an example taken from this answer:

NSManagedObjectContext * context = [self managedObjectContext];
NSFetchRequest * fetch = [[[NSFetchRequest alloc] init] autorelease];
[fetch setEntity:[NSEntityDescription entityForName:@"ShoppingBasket" inManagedObjectContext:context]];
NSArray * result = [context executeFetchRequest:fetch error:nil];
for (id basket in result)
    [context deleteObject:basket];

So get the context, Create a search, get an array from the context based on the search criteria, loop through the results and do as you will with updating them.

edited May 23, 2017 at 12:19

CommunityBot

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answered Jan 7, 2014 at 2:19

Putz1103

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2 Comments

Duncan Groenewald Over a year ago

Presumably he has already done a fetch with the fetchedResultsController so no point in doing another fetch. See my answer to use the existing fetchedResultsController result set.

Putz1103 Over a year ago

I agree that duplicate fetches would be rather stupid and time wasting. Thanks for the information, if I ever get into core data it will come in handy.

Duncan Groenewald · Accepted Answer · 2014-01-07 02:50:59Z

1

If you are using a fetchedResultsController already to populate the tableView then you can iterate over the objects in the fetchedResultsController like this:

- (IBAction)allDoneAction:(id)sender {

    NSArray *objects = [fetchedResultsController fetchedObjects];

    for (NSManagedObject *mo in objects) {
       [mo setValue:@"Done" forKey:@"isDone"];i++;
    }

    NSError *error;
    bool result = [[fetchedResultsController managedObjectContext] save:&error];

    if (!result) {
       NSLog(@" error saving context, %@, %@", error, error.userInfo);
    }

}

BTW you should be checking for errors in your call to save so don't pass in nil.

edited Jan 7, 2014 at 2:50

answered Jan 7, 2014 at 2:35

Duncan Groenewald

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3 Comments

mvasco Over a year ago

Yes, I am populating the tableView using a fetchedResultsController. Your proposal, adding int i=0; shows a warning at 'fetchResults' and an exception at execution: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSFetchedResultsController fetchedResults]: unrecognized selector sent to instance

Duncan Groenewald Over a year ago

post the code you are using to create the fetchedResultsController

Duncan Groenewald Over a year ago

No, don't bother I made a mistake its fetchedObjects not fetchedResults, see the corrected code.

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