iOS: Core Data: NSRangeException en exemple simple

Question

J'ai fait simple base de données Exemple:

NSLog(@"Loading..."); 
NSURL *modelUrl = [[NSBundle mainBundle] URLForResource:@"CoreDataTest" withExtension:@"momd"]; 
NSManagedObjectModel *objectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelUrl];  
NSManagedObjectContext *objectContext = [[NSManagedObjectContext alloc] init]; 

NSError *error = nil; 

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *documentsDirectory = [paths objectAtIndex:0]; 
NSURL *storeUrl = [NSURL fileURLWithPath:[documentsDirectory stringByAppendingPathComponent:@"DB.sqlite"]]; 
NSPersistentStoreCoordinator *coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:objectModel]; 
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: 
         [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, 
         [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; 
NSPersistentStore *migratedStore = [coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]; 
if(migratedStore == nil) { 
    NSLog(@"Could not initialize or migrate store: %@", [error localizedDescription]); 
} 

[objectContext setPersistentStoreCoordinator:coordinator]; 

MyQueuedJob *queuedJob = (MyQueuedJob *) [NSEntityDescription insertNewObjectForEntityForName:@"MyQueuedJob" inManagedObjectContext:objectContext]; 
queuedJob.fooBar = @"Test"; 

[objectContext save:&error]; 
sleep(2); 

NSFetchRequest *request = [NSFetchRequest alloc]; 
NSEntityDescription *entDesc = [NSEntityDescription entityForName:@"MyQueuedJob" inManagedObjectContext:objectContext]; 
[request setEntity:entDesc]; 
NSSortDescriptor *sortDesc = [[NSSortDescriptor alloc] initWithKey:@"fooBar" ascending:YES]; 
[request setSortDescriptors:[[NSArray alloc] initWithObjects:sortDesc, nil]]; 
NSLog(@"fetching jobs..."); 
NSArray *fetchResults = [objectContext executeFetchRequest:request error:nil]; 
NSLog(@"jobs fetched!"); 
NSLog(@"%@", [fetchResults componentsJoinedByString:@", "]); 

Code de MyQueuedJob.h (généré par Xcode):

@interface MyQueuedJob : NSManagedObject 

@property (nonatomic, retain) NSString * fooBar; 

@end 

Cet exemple fonctionne parfaitement bien dans le simulateur. Mais quand je le lance sur mon vrai iPhone 4, il se bloque avec le message suivant:

2012-02-16 11:06:44.819 CoreDataTest[345:707] Loading... 
2012-02-16 11:06:46.937 CoreDataTest[345:707] fetching jobs... 
2012-02-16 11:06:46.950 CoreDataTest[345:707] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array' 

sur cette ligne:

NSArray *fetchResults = [objectContext executeFetchRequest:request error:nil]; 

Qu'est-ce que je fais mal?

Answer 1

NSFetchRequest *request = [NSFetchRequest alloc]; 

Vous devez init init this. Changez-le en [[NSFetchRequest alloc] init];