Why Isn't Core Data Fetching My Data?

Question

My data for for an entity\'s attribute is not being fetched upon restart or not being saved before quitting (could be either case). The bottom line is, the data is not showing

Answer 1

Have you attached your core data file in your Main Bundle? There are two types of Bundle in iPhone app. Main Bundle and Application Bundle. We had a scenario something like yours. We copied the database into our main bundle and write the location of the database into our code. then it worked fine. you can check on this issue also.

Answer 2

Here's a couple of tips to fix this :

1. Remove all references to managedObjectContext, etc. in your RoutineViewController. Only reference the CoreData classes / properties from your AppDelegate.
2. Whenever you need a reference (say in your AddEvent method) reference the appropriate objects from your delegate (see code below)

3. When this gets more complex, you'll probably want a DataManager class that handles ALL your CoreData objects. Make it a Singleton, and you'll be able to reference it in any class. For fetching objects for display, you can then create the necessary methods in this class to retrieve these objects in a NSMutableArray

   CurlAppDelegate *curlAppDelegate = [[UIApplication sharedApplication] delegate]; NSManagedObjectContext *context = [curlAppDelegate managedObjectContext];

   Routine *routine = (Routine *)[NSEntityDescription insertNewObjectForEntityForName:@"Routine" inManagedObjectContext:context];

See how you're now using the context from your AppDelegate and not locally? This is important, because your app will link your xdatamodel from your Bundle into your AppDelegate on initialization.

If you're concerned about the data not being saved, or overwritten, check out your AppDelegate's - (NSPersistentStoreCoordinator *)persistentStoreCoordinator

That's where the setup happens to link to your stored database when you exit and enter the app. Here's your code (modified) in your AppDelegate that loads in the Curl.sqlite file :

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator{
if (__persistentStoreCoordinator != nil)
{
    return __persistentStoreCoordinator;
}

NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Curl.sqlite"];

NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
{

    NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    abort();
}    

return __persistentStoreCoordinator;

}

Answer 3

My guess would be that your are mixing up your managed object contexts. Inserting into one and attempting to save on another. Remove your Core Data associated methods in your view controller and just try going through your app delegate methods. The data will either then be saved correctly, or an error will be tossed by Core Data. Make sure to inspect any setup/save errors in your Core Data code.