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    <p>Your managed object context is probably not set and the entity "Event" is obviously not valid for a nil context. </p> <p>I use a reference to my app delegate in all my view controllers so they can access the one managed object context. It sounds like others often use a singleton to manage Core Data and would get the managed object context from that.</p> <p><strong>UPDATE</strong></p> <p>There is a good discussion about where to keep the Core Data stack in <a href="https://stackoverflow.com/questions/1267520/where-to-place-the-core-data-stack-in-a-cocoa-cocoa-touch-application">Where to place the “Core Data Stack” in a Cocoa/Cocoa Touch application</a>. </p> <p>Here is some example code for keeping the Core Data stack in the app delegate:</p> <p>Use Apple's standard Core Data stack implementation in YourAppDelegate. managedObjectContext is implemented as an example, but managedObjectModel and persistentStoreCoordinator must be implemented as well.</p> <p><strong>YourAppDelegate.h</strong>:</p> <pre><code>@interface YourAppDelegate : NSObject &lt;UIApplicationDelegate&gt; { // Core Data stuff NSManagedObjectModel *managedObjectModel; NSManagedObjectContext *managedObjectContext; NSPersistentStoreCoordinator *persistentStoreCoordinator; // other app ivars } </code></pre> <p><strong>YourAppDelegate.m</strong>:</p> <pre><code>- (NSManagedObjectContext *) managedObjectContext { if (managedObjectContext != nil) { return managedObjectContext; } NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; if (coordinator != nil) { managedObjectContext = [[NSManagedObjectContext alloc] init]; [managedObjectContext setPersistentStoreCoordinator: coordinator]; } return managedObjectContext; } </code></pre> <p>In every view controller, get a reference to the app delegate and use it to get the managedObjectContext as needed. For example, when setting up the fetchedResultsController;</p> <p><strong>RootViewController.h</strong>:</p> <pre><code>@interface RootViewController : UITableViewController &lt;NSFetchedResultsControllerDelegate&gt; { NSFetchedResultsController *fetchedResultsController; YourAppDelegate *app; } </code></pre> <p><strong>RootViewController.m</strong>:</p> <pre><code>#import "RootViewController.h" #import "YourAppDelegate.h" @implementation RootViewController @synthesize fetchedResultsController; - (void)viewDidLoad { [super viewDidLoad]; app = (YourAppDelegate*)[UIApplication sharedApplication].delegate; } - (NSFetchedResultsController *)fetchedResultsController { if (fetchedResultsController != nil) { return fetchedResultsController; } NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:app.managedObjectContext]; [fetchRequest setEntity:entity]; // setup the batch size, predicate, &amp; sort keys, etc NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:app.managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; [aFetchedResultsController release]; [fetchRequest release]; return fetchedResultsController; } </code></pre>
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    1. COcan you give me an example of how you do it?
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    2. COAnswer has been updated with some example code.
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