SearchBar crashes after first character -Core Data

Question

Whenever I attempt to enter a second character into the SearchBar the app crashes with a "terminating with uncaught exception" error. The SearchBar is referencing the Table Cell data if that helps at all. How do I fix this?

@interface DeviceViewController ()
@property (strong) NSMutableArray *devices;
@end

@implementation DeviceViewController
{
    NSArray *searchResults;
}
- (NSManagedObjectContext *)managedObjectContext {
    NSManagedObjectContext *context = nil;
    id delegate = [[UIApplication sharedApplication] delegate];
    if ([delegate performSelector:@selector(managedObjectContext)]) {
        context = [delegate managedObjectContext];
    }
    return context;
}
- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];
    //label.backgroundColor = [UIColor clearColor];
    label.font = [UIFont fontWithName:@"HelveticaNeue-thin" size:28];
    //label.shadowColor = [UIColor colorWithWhite:0.0 alpha:0.5];
    label.textColor = [UIColor blackColor];
    self.navigationItem.titleView = label;
    label.text = @"TapNotes";
    [label sizeToFit];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    // Fetch the devices from persistent data store
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Device"];
    self.devices = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];

    [self.tableView reloadData];
}

- (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 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (tableView == self.searchDisplayController.searchResultsTableView) {
        return [searchResults count];

    } else {
        return self.devices.count;
    }
    //return self.devices.count;
    }
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell==nil) {
        cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier]; }
    NSManagedObject *device = [self.devices objectAtIndex:indexPath.row];
    [cell.textLabel setText:[NSString stringWithFormat:@"%@", [device valueForKey:@"name"]]];
    [cell.detailTextLabel setText:[NSString stringWithFormat:@"%@",[device valueForKey:@"version"]]];
    if (tableView == self.searchDisplayController.searchResultsTableView) {
        device = [searchResults objectAtIndex:indexPath.row];
    } else {
        [self.devices objectAtIndex:indexPath.row];
    }

   // cell.thumbnailImageView.image = [UIImage imageNamed:recipe.image];

    return cell;
}
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the specified item to be editable.
    return YES;
}


- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObjectContext *context = [self managedObjectContext];

    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete object from database
        [context deleteObject:[self.devices objectAtIndex:indexPath.row]];

        NSError *error = nil;
        if (![context save:&error]) {
            NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]);
            return;
        }

        // Remove device from table view
        [self.devices removeObjectAtIndex:indexPath.row];
        [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }
}

/*
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // 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.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/

/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the item to be re-orderable.
    return YES;
}
*/
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"UpdateDevice"]) {
        NSManagedObject *selectedDevice = [self.devices objectAtIndex:[[self.tableView indexPathForSelectedRow] row]];
         NSIndexPath *indexPath = nil;
        if (self.searchDisplayController.active) {
            indexPath = [self.searchDisplayController.searchResultsTableView indexPathForSelectedRow];
            _devices = [searchResults objectAtIndex:indexPath.row];
        } else {
            indexPath = [self.tableView indexPathForSelectedRow];
            _devices = [_devices objectAtIndex:indexPath.row];
        }
        DeviceDetailViewController *destViewController = segue.destinationViewController;
        destViewController.device = selectedDevice;
    }
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 55;
}
- (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
{
    NSPredicate *resultPredicate = [NSPredicate predicateWithFormat:@"name contains[c] %@", searchText];
    searchResults = [_devices filteredArrayUsingPredicate:resultPredicate];
}
-(BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
{
    [self filterContentForSearchText:searchString
                               scope:[[self.searchDisplayController.searchBar scopeButtonTitles]
                                      objectAtIndex:[self.searchDisplayController.searchBar
                                                     selectedScopeButtonIndex]]];

    return YES;
}
@end

Answer 1

You have many table view managing issues.

As I mentioned HERE, Use a NSFetchedResultsController (or open an empty project that include CoreData and see how easy table management will be when you have one).

You can't filter your search array without notifying the table that it needs to be reloaded.
The table view must know the count of the datasource as it will expect this data to exist when it asks for it in cellForRow...

Also, you treat your _device variable once as an NSArray and one as a managed object (in cellForRow...).

in cellForRow... change _device to device ...
and then you will have a new problem ...

(look at the advices I gave you in your previous question)