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POAdding CoreData to existing iOS project - can't get NSManagedObjectModel
 

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  1. POAdding CoreData to existing iOS project - can't get NSManagedObjectModel
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    <p>I am trying to add CoreData to an existing iOS application, created in Xcode 4.2. As it's tab bar based app, I wasn't given the option of including it by default at creation time.</p> <p>So far I've:</p> <ul> <li>Added the CoreData.framework to the app (confirmed in build target)</li> <li>Added a model 'model.coredatamodeld' (confirmed in build target, confirmed that the 'mom' file is included in the application directory while running in the iOS simulator)</li> <li>Replaced the app delegate with the autogenerated version from a fresh CoreData enabled app</li> </ul> <p>I end up with the object model creation returning nil. If I look at the URL produced, it is sensible and points at the 'mom' folder in my filesystem. The folder contains 'model.momd' and 'VersionInfo.plist'. Both files have sensible looking contents (the former is some binary data, the later some reasonable sounding XML). </p> <pre><code>__managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL: modelURL]; // __managedObjectModel is nil here </code></pre> <p>How to debug this?</p> <p>Source for App delegate below.</p> <pre><code>#import "AppDelegate.h" #import &lt;CoreData/CoreData.h&gt; @implementation AppDelegate @synthesize window = _window; @synthesize managedObjectContext = __managedObjectContext; @synthesize managedObjectModel = __managedObjectModel; @synthesize persistentStoreCoordinator = __persistentStoreCoordinator; - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after application launch. id ctx = self.managedObjectContext; //id model = [self managedObjectModel]; //NSLog(@"%@ %@", ctx, model); return YES; } - (void)applicationWillTerminate:(UIApplication *)application { // Saves changes in the application's managed object context before the application terminates. [self saveContext]; } - (void)saveContext { NSError *error = nil; NSManagedObjectContext *managedObjectContext = self.managedObjectContext; if (managedObjectContext != nil) { if ([managedObjectContext hasChanges] &amp;&amp; ![managedObjectContext save:&amp;error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } } } #pragma mark - Core Data stack /** Returns the managed object context for the application. If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application. */ - (NSManagedObjectContext *)managedObjectContext { if (__managedObjectContext != nil) { return __managedObjectContext; } NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; if (coordinator != nil) { __managedObjectContext = [[NSManagedObjectContext alloc] init]; [__managedObjectContext setPersistentStoreCoordinator:coordinator]; } return __managedObjectContext; } /** Returns the managed object model for the application. If the model doesn't already exist, it is created from the application's model. */ - (NSManagedObjectModel *)managedObjectModel { if (__managedObjectModel != nil) { return __managedObjectModel; } NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"model" withExtension:@"momd"]; __managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL: modelURL]; NSError *error = nil; NSData *objectIDData = [NSData dataWithContentsOfURL:modelURL options:NSDataReadingMapped error:&amp;error]; NSLog(@"%@",objectIDData); return __managedObjectModel; } /** Returns the persistent store coordinator for the application. If the coordinator doesn't already exist, it is created and the application's store added to it. */ - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (__persistentStoreCoordinator != nil) { return __persistentStoreCoordinator; } NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"model.sqlite"]; NSError *error = nil; __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&amp;error]) { /* Replace this implementation with code to handle the error appropriately. abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. Typical reasons for an error here include: * The persistent store is not accessible; * The schema for the persistent store is incompatible with current managed object model. Check the error message to determine what the actual problem was. If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory. If you encounter schema incompatibility errors during development, you can reduce their frequency by: * Simply deleting the existing store: [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil] * Performing automatic lightweight migration by passing the following dictionary as the options parameter: [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details. */ NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return __persistentStoreCoordinator; } #pragma mark - Application's Documents directory /** Returns the URL to the application's Documents directory. */ - (NSURL *)applicationDocumentsDirectory { return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]; } @end </code></pre>
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