A set of simple wrapper functions to get per-thread NSManagedObjectContext instances. When creating main context (i.e. in app delegate) pass it to StoreManagedObjectContextForCurrentThread(). Then just call PerThreadManagedObjectContext() anywhere you nee

AQPerThreadManagedObjectContext.m

static NSString * const AQPerThreadManagedObjectContext = @"AQPerThreadManagedObjectContext";

void StoreManagedObjectContextForCurrentThread( NSManagedObjectContext * context )
{
    [[[NSThread currentThread] threadDictionary] setObject: context forKey: AQPerThreadManagedObjectContext];
}

NSManagedObjectContext * PerThreadManagedObjectContext( void )
{
    NSManagedObjectContext * result = [[[NSThread currentThread] threadDictionary] objectForKey: AQPerThreadManagedObjectContext];
    if ( result != nil )
        return ( result );
    
    NSManagedObjectContext * moc = [[NSManagedObjectContext alloc] init];
	[moc setMergePolicy: NSMergeByPropertyObjectTrumpMergePolicy];
    [moc setPersistentStoreCoordinator: GetPersistentStoreCoordinator()];
    StoreManagedObjectContextForCurrentThread( moc );
    [moc release];      // now owned by the thread dictionary
    
    return ( moc );
}