core data multithread using - objective-c

Question

Dear community.
When i has a stable version of my application, while i don't start change code to multithread version. What was a difference between previous version:
in (void)applicationDidFinishLaunching:(NSNotification *)aNotification
i do loop to add to queue my code:
NSOperationQueue *opQueueImportUpdateFirstTimeData = [[[NSOperationQueue alloc]init]autorelease];
int i = 0;
for (NSString *carrier in currentCarriers)
{
AppController *operation = [[AppController alloc] initAndUpdateCarrier:carrier identifier:i];
[opQueueImportUpdateFirstTimeData addOperation:operation];
i++;
}
External class have:
- (id)initAndUpdateCarrier:(NSString *)forCarrier
identifier:(NSUInteger)iQuene;
{
[super init];
[self setIdentifierQuene:iQuene];
[self setStartForCarrier:forCarrier];
[self setPercentDone:0.0];
This point is a very important:
[self setDatabase:[[MySQLIXC alloc] init]];
u can't alloc other classes in process of u multithreading, i don't know why, but this is take malloc_error in whole queues
[self setAppDelegate:[[NSApplication sharedApplication] delegate]];
[self setManagedObjectContext:[[NSManagedObjectContext alloc] init]];
return self;
}
And in external class i have:
-(void) main;
{
[self makeUpdatesForCarrier:startForCarrier andTypeOfOperation:#"rates" forDirection:#"incoming"];// mySqlConnector:database];
it's a just some functions which working on local moc.
When i start application, interface didn't place it in background, and start visualization only after all queues will finish.
Before i try to alloc]init] MySQLIXC class inside my external class, but it gives me a lot of malloc_error_break exceptions, like somebody try to freeze memory for me.
Tnx.
Here is moc declaration:
in .h:
#property(retain) NSManagedObjectContext *managedObjectContext;
in .m:
#synthesize managedObjectContext;
Set persistent store coordinator:
[[self managedObjectContext] setUndoManager:nil];
[[self managedObjectContext] setPersistentStoreCoordinator:[appDelegate persistentStoreCoordinator]];
Merge changes for with main moc:
- (void)mergeChanges:(NSNotification *)notification;
{
AppDelegate *appDelegate = [[NSApplication sharedApplication] delegate];
NSManagedObjectContext *mainContext = [appDelegate managedObjectContext];
// Merge changes into the main context on the main thread
[mainContext performSelectorOnMainThread:#selector(mergeChangesFromContextDidSaveNotification:)
withObject:notification
waitUntilDone:YES];
And in one place of my code i'm using a main moc (only for read information, i know that moc not thread safe):
AppDelegate *appDelegate = [[NSApplication sharedApplication] delegate];
NSManagedObjectContext *mainContext = [appDelegate managedObjectContext];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:[NSEntityDescription entityForName:#"DestinationsListForSale"
inManagedObjectContext:mainContext]];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"lastUsedProfit > 0"];
[request setPredicate:predicate];

Answer 1

First off, CoreData is NOT thread safe. I would strongly advise that if you do not understand core data in a good deal of detail you keep you application singlethreaded or at the very least ensure that you always access the store from a single thread (probably best to use the main thread).
That said, this will not cause malloc_error_breaks AFAIK. You would see core data merge error exceptions and similar problems.
Could you show the code where you set up the moc further - just allocating and initing a moc is not enough - you have to set it's NSPersistentStoreCoordinator