IPhone - Crash in core data - multiple managed object context - iphone

Question

So, i'm using core data with multiple thread. each one gets his own Managed object context.
I get an unrecognized selector exception , so I'm curious if I'm doing something wrong.
The crash is obviously related to the "mergeChanges" method.
I would greatly appreciate any help.
Edit
The problem seems to be that the myManagedObjectContext returns a deallocated object.
How could that be ?
My code:
- (NSManagedObjectContext *) myManagedObjectContext {
NSManagedObjectContext * result = [[[NSThread currentThread] threadDictionary] objectForKey: AQPerThreadManagedObjectContext];
if ( result != nil )
return result;
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator!=nil)
{
NSManagedObjectContext * moc = [[NSManagedObjectContext alloc] init];
[moc setMergePolicy: NSMergeByPropertyObjectTrumpMergePolicy];
[moc setPersistentStoreCoordinator: coordinator];
[self StoreManagedObjectContextForCurrentThread:moc];
[moc release]; // now owned by the thread dictionary
return moc ;
}
else {
GTMLoggerError(#"FAILED TO return managed object context ");
}
return nil;
}
-(void) StoreManagedObjectContextForCurrentThread:(NSManagedObjectContext*) context
{
[[[NSThread currentThread] threadDictionary] setObject: context forKey: AQPerThreadManagedObjectContext];
}
-(BOOL) saveChanges
{
BOOL success = YES;
NSManagedObjectContext* moc = [self myManagedObjectContext];
NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
[nc addObserver:self
selector:#selector(mergeChanges:)
name:NSManagedObjectContextDidSaveNotification
object:moc];
NSError *error = nil;
if ([moc save:&error] == NO)
{
success = NO;
GTMLoggerError(#"Failed to save to data store: [%#], [%#]",
[error localizedDescription],
[error userInfo]);
}
return success;
}
- (void)mergeChanges:(NSNotification *)notification
{
NSManagedObjectContext* moc = [self myManagedObjectContext];
AppDelegate * delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *mainContext = [delegate mainThreadMOC];
// Merge changes into the main context on the main thread
[mainContext performSelectorOnMainThread:#selector(mergeChangesFromContextDidSaveNotification:)
withObject:notification
waitUntilDone:YES];
NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
[nc removeObserver:self name:NSManagedObjectContextDidSaveNotification object:moc];
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
mainThreadMOC = [[NSManagedObjectContext alloc]init];
[mainThreadMOC setMergePolicy: NSMergeByPropertyObjectTrumpMergePolicy];
[mainThreadMOC setPersistentStoreCoordinator: [[DatabaseManager sharedManager] persistentStoreCoordinator]];
[[DatabaseManager sharedManager] StoreManagedObjectContextForCurrentThread:mainThreadMOC];
.....
.....
}
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSKeyPathExpression _processReferenceQueue:]: unrecognized selector sent to instance 0xa65940'
0 CoreFoundation 0x3587a987 __exceptionPreprocess + 114
1 libobjc.A.dylib 0x34a8249d objc_exception_throw + 24
2 CoreFoundation 0x3587c133 -[NSObject(NSObject) doesNotRecognizeSelector:] + 102
3 CoreFoundation 0x35823aa9 ___forwarding___ + 508
4 CoreFoundation 0x35823860 _CF_forwarding_prep_0 + 48
5 CoreData 0x356ea3d5 -[NSManagedObjectContext(_NSInternalNotificationHandling) _processReferenceQueue:] + 24
6 CoreData 0x3573032b -[NSManagedObjectContext mergeChangesFromContextDidSaveNotification:] + 842
7 CoreFoundation 0x35818bbf -[NSObject(NSObject) performSelector:withObject:] + 22
8 Foundation 0x31181795 __NSThreadPerformPerform + 268
9 CoreFoundation 0x358307dd __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 12
10 CoreFoundation 0x358025b7 __CFRunLoopDoSources0 + 382
11 CoreFoundation 0x35801e5b __CFRunLoopRun + 230
12 CoreFoundation 0x35801c87 CFRunLoopRunSpecific + 230
13 CoreFoundation 0x35801b8f CFRunLoopRunInMode + 58
14 GraphicsServices 0x320c84ab GSEventRunModal + 114
15 GraphicsServices 0x320c8557 GSEventRun + 62
16 UIKit 0x341dc329 -[UIApplication _run] + 412
17 UIKit 0x341d9e93 UIApplicationMain + 670

Answer 1

Not sure if this is the problem, but you should always return autoreleased-values from a function.
You're doing:
[moc release]; // now owned by the thread dictionary
return moc ;
but regardless of the ownership in the thread-dictionary, it should be:
return [moc autorelease];