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PONSFetchedResultsController returning objects with null indexPaths
 

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    <p>Details are in the comments.</p> <p>The following code:</p> <pre><code>// Perform the fetch... NSError *error = nil; if (![[self fetchedResultsController] performFetch:&amp;error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } // Confirm that objects were fetched by counting them... NSLog(@"Number of Objects = %i", [[fetchedResultsController fetchedObjects] count]); // Confirm that sections exist by counting them... NSLog(@"Numbers of Sections = %i", [[fetchedResultsController sections] count]); for (id section in [fetchedResultsController sections]) { // Count number of objects in each section // _The fact that this outputs 0 is the first sign of trouble_ NSLog(@"Number of Objects in Section = %i", [section numberOfObjects]); } for (Reminder *reminder in [fetchedResultsController fetchedObjects]) { // Confirm that the objects fetched are in fact real objects // by accessing their "textContent" property... NSLog(@"textContent=%@", reminder.textContent); // Show that the fetched objects are being returned // with a (null) indexPath... // _The second sign of trouble..._ NSLog(@"IndexPath=%@", [fetchedResultsController indexPathForObject:reminder]); } NSUInteger indexArr[] = {0,0}; NSIndexPath *indexPath = [NSIndexPath indexPathWithIndexes:indexArr length:2]; // _Application crashes on this line because the fetched // objects do not have indexPaths_ Reminder *testReminder = (Reminder *)[fetchedResultsController objectAtIndexPath:indexPath]; NSLog(@"textContent = %@", testReminder.textContent); </code></pre> <p>Results in the following output:</p> <pre><code>2010-07-17 00:48:41.865 Reminders[27335:207] Number of Objects = 3 2010-07-17 00:48:41.867 Reminders[27335:207] Numbers of Sections = 1 2010-07-17 00:48:41.868 Reminders[27335:207] Number of Objects in Section = 0 2010-07-17 00:48:41.870 Reminders[27335:207] textContent=Imported Object 3 2010-07-17 00:48:41.871 Reminders[27335:207] IndexPath=(null) 2010-07-17 00:48:41.873 Reminders[27335:207] textContent=Imported Object 2 2010-07-17 00:48:41.873 Reminders[27335:207] IndexPath=(null) 2010-07-17 00:48:41.874 Reminders[27335:207] textContent=Imported Object 1 2010-07-17 00:48:41.875 Reminders[27335:207] IndexPath=(null) 2010-07-17 00:48:41.887 Reminders[27335:207] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0)' </code></pre> <p>Any ideas would be greatly appreciated. FYI, the above code works perfectly in a separate application if I use a different template as a starting point. I.e. if I use the "Window-based application" template, the code will fail. If I use "Navigation-based application" the code works as expected.</p> <p><strong>Update:</strong> TechZen was wondering if the problem is caused by my Reminder entity. I thought this was a good idea to look into, so I did the following:</p> <ol> <li><p>Create two default template applications: a "Window-based application" and a "Navigation-based Application" (both with Core Data enabled)</p></li> <li><p>Copied over the minimum code needed from the Nav-based to the Window-based to perform the above test (pretty much just the "xcdatamodel" file, the fetchedresultscontroller, and a way to add test objects).</p></li> </ol> <p>The above code still fails in the new "Reminder-entity free" window-based application. (In this new test application there is in fact zero code I've authored myself (outside of the test code), it's all just template code cut-and-pasted together.)</p> <p>So now, I am looking for <em>any way</em> to get the above code to run after creating a "Window-based application". Here is the code to perform the test using the nav-based's default entity, in case anyone is interested in giving it a try:</p> <p><strong>UPDATE</strong> Note that as TechZen noted below this code will crash no matter what if run with an empty database, so if starting from a window-based application, first add a few objects to the database then add the test code.</p> <pre><code>// Confirm that objects were fetched NSLog(@"Number of Objects = %i", [[fetchedResultsController fetchedObjects] count]); // Confirm that sections exist NSLog(@"Numbers of Sections = %i", [[fetchedResultsController sections] count]); for (id section in [fetchedResultsController sections]) { // Count number of objects in sections // _The fact that this outputs 0 is the first sign of trouble_ NSLog(@"Number of Objects in Section = %i", [section numberOfObjects]); } for (NSManagedObject *managedObject in [fetchedResultsController fetchedObjects]) { // Confirm that the objects fetched are in fact real objects, // by accessing their "timeStamp" property NSLog(@"TimeStamp=%@", [[managedObject valueForKey:@"timeStamp"] description]); // Show that the fetched objects are being returned // with a (null) indexPath // _The second sign of trouble..._ NSLog(@"IndexPath=%@", [fetchedResultsController indexPathForObject:managedObject]); } NSUInteger indexArr[] = {0,0}; NSIndexPath *indexPath = [NSIndexPath indexPathWithIndexes:indexArr length:2]; // _Application crashes on this line, because the fetched // objects do not have indexPaths_ NSManagedObject *managedObject = [fetchedResultsController objectAtIndexPath:indexPath]; NSLog(@"textContent = %@", [[managedObject valueForKey:@"timeStamp"] description]); </code></pre> <p><strong>UPDATE</strong> here is the output when using the new cut-and-pasted code</p> <pre><code>2010-07-18 15:33:41.264 Reminders[30898:207] Number of Objects = 3 2010-07-18 15:33:41.266 Reminders[30898:207] Numbers of Sections = 1 2010-07-18 15:33:41.267 Reminders[30898:207] Number of Objects in Section = 0 2010-07-18 15:33:41.270 Reminders[30898:207] TimeStamp=2010-07-18 13:59:00 -0400 2010-07-18 15:33:41.271 Reminders[30898:207] IndexPath=(null) 2010-07-18 15:33:41.272 Reminders[30898:207] TimeStamp=2010-07-18 13:59:00 -0400 2010-07-18 15:33:41.273 Reminders[30898:207] IndexPath=(null) 2010-07-18 15:33:41.274 Reminders[30898:207] TimeStamp=2010-07-18 13:58:59 -0400 2010-07-18 15:33:41.275 Reminders[30898:207] IndexPath=(null) 2010-07-18 15:33:41.276 Reminders[30898:207] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0)' </code></pre> <p><strong>UPDATE</strong> So I narrowed this problem down to being an SDK version-related issue, I now have a project that if I build with Simulator 3.2 it crashes, and build with Simulator 3.1.3 it works fine. BUT if I add a UITableViewController, then build with Simulator 3.2, then it works fine again. So I've created a <a href="https://stackoverflow.com/questions/3277415/using-an-nsfetchedresultscontroller-without-a-uitableviewcontroller">new stackoverflow</a> post to ask the question: If you are using NSFetchedResultsController without a UITableViewController, how do you interact with the objects? (since the IndexPaths are unreliable).</p> <p><strong>UPDATE</strong> This issue is (tentatively) solved by using -<code>[NSFetchedResultsController fetchedObjects] objectAtIndex:]</code> to access the objects.</p>
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