Question

When my application first runs I’m using some simple code to read in some data from a source and then saving it to core data to be read back in the future. Here is my applicationDidFinishLaunching method:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    categories = [[NSMutableArray alloc] init];
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    if (![defaults objectForKey:@"dataImported"]) {
        NSMutableArray *temp_Categories = [[NSMutableArray alloc] initWithObjects:@"Food & Drink", @"Medical", @"Hotel", @"Travel", nil];

        for(int i = 0; i < [temp_Categories count]; i++){
            //Insert a new object of type ProductInfo into Core Data
            NSManagedObject *categoryInfo = [NSEntityDescription
                                              insertNewObjectForEntityForName:@"Category" 
                                              inManagedObjectContext:self.managedObjectContext];

            //Set category entities values
            [categoryInfo setValue:[temp_Categories objectAtIndex:i] forKey:@"categoryName"];

            [categories addObject:[temp_Categories objectAtIndex:i]];
        }

        [defaults setObject:@"OK" forKey:@"dataImported"];
        [defaults synchronize];

        NSLog(@"Imported");
    }
    else {
        //read from core data
        NSError *error;
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        NSEntityDescription *entity = [NSEntityDescription 
                                       entityForName:@"Category" inManagedObjectContext:self.managedObjectContext];
        [fetchRequest setEntity:entity];
        NSMutableArray *temp_Categories = [[NSMutableArray alloc] initWithArray:[self.managedObjectContext executeFetchRequest:fetchRequest error:&error]];

        for (int i = 0; i < [temp_Categories count]; i++){
            NSString *category = [[temp_Categories objectAtIndex:i] objectForKey:@"categoryName"];
            [categories addObject:category];
            NSLog(@"Success");
        }

        NSLog(@"Read From Core");
    }

    return YES;
}

When I run this code the very first time, it works correctly, however when I run it in future (when it read from core data) it does not work, it doesn’t read in the array from core data and temp_Categories count = 0. Can anyone explain what I’m doing wrong? I’m having the same trouble trying to do the same thing with a plist file in another app.

Thanks,

Jack

EDIT 1 I’m using iOS 5.

EDIT 2 Data model screenshot:

Answer 1

I managed to get it to work with this:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    categories = [[NSMutableArray alloc] init];
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    if (![defaults objectForKey:@"dataImported"]) {
        NSMutableArray *temp_Categories = [[NSMutableArray alloc] initWithObjects:@"Food & Drink", @"Medical", @"Hotel", @"Travel", nil];

        for(int i = 0; i < [temp_Categories count]; i++){
            //Insert a new object of type Category into Core Data
            NSManagedObject *categoryInfo = [NSEntityDescription
                                             insertNewObjectForEntityForName:@"Category" 
                                             inManagedObjectContext:self.managedObjectContext];

            //Set category entities values
            [categoryInfo setValue:[temp_Categories objectAtIndex:i] forKey:@"name"];

            NSError *error;
            if (![self.managedObjectContext save:&error]) {
                NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
            }

            NSLog(@"Added category to Core Data");

            //Add to global array
            [categories addObject:[temp_Categories objectAtIndex:i]];
        }

        [defaults setObject:@"OK" forKey:@"dataImported"];
        [defaults synchronize];

        NSLog(@"Imported");
    }
    else {
        //read from core data
        NSError *error;
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        NSEntityDescription *entity = [NSEntityDescription 
                                       entityForName:@"Category" inManagedObjectContext:self.managedObjectContext];
        [fetchRequest setEntity:entity];
        NSMutableArray *temp_Categories = [[NSMutableArray alloc] initWithArray:[self.managedObjectContext executeFetchRequest:fetchRequest error:&error]];

        for (NSManagedObject *object in temp_Categories){
            [categories addObject: [object valueForKey:@"name"]];
        }

        NSLog(@"Read From Core");
    }

    return YES;
}

Thanks for all your help.