Can not read data using NSManagedObjectContext - objective-c

Question

I am trying to read an array from Core Data. My code is as follows
-(NSArray *)getAges
{
NSArray *fetchedObjects = [[NSArray alloc] init];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSManagedObjectContext *context = nil;
context = [[NSManagedObjectContext alloc] init];
#try {
NSPersistentStoreCoordinator *tempCordinator = (NSPersistentStoreCoordinator *)[(AppDelegate *)[[UIApplication sharedApplication] delegate] persistentStoreCoordinator];
[context setPersistentStoreCoordinator:tempCordinator];
NSError *error;
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Age"
inManagedObjectContext:context];
[fetchRequest setEntity:entity];
fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
}
#catch (NSException *exception) {
NSLog(#"core data exception occured.");
fetchedObjects = nil;
}
[fetchRequest release];
[context release];
return fetchedObjects;
}
Now in main thread, in an IBAction method, I write following line.
[NSThread detachNewThreadSelector:#selector(loadAgesMethod) toTarget:self withObject:nil];
Problem is that this method returns me an array of 20 elements. I can see the array count 20 but in debugger, against every element of array, i see 'out of scope' and 'summary unavailable'. And when I try to fetch any object from this array, i get nothing. One thing is to mention is that I am calling this method getAges in loadAgesMethod from a secondary thread as I mentioned above. This is my requirement. Also when I try to retrieve this array from main thread, i get all data perfectly ok.
Can anyone please give me a hint, where I am wrong?
Best regards

Answer 1

Every NSManagedObject has a NSManagedObjectContext property. This is used to lazily fetch properties of the object when required in the future. At the end of this method you call [context release] hence the NSManagedObjectContext will be deallocated and all your NSManagedObject context properties will be nil for your Age objects.
You could call [context autorelease] on the context so that it persists for some time after the method and allows you to fetch properties on the objects at a later stage. Note this will only persist until the autorelease pool drains at the end of the run loop. I am still trying myself to come up with a better solution to multithreaded fetching.