gistfile1.m

- (void)update:(void (^)(void))block
{    
    __unsafe_unretained NUData* wself = self; 
    dispatch_queue_t caller = dispatch_get_current_queue();
    
    dispatch_async(queue, ^{
        NSLog(@"updating");
        // dispatch these tasks concurrently, wait the queue until done
        dispatch_queue_t async_tasks_queue = dispatch_queue_create("com.ft.update.async", DISPATCH_QUEUE_CONCURRENT);
        dispatch_group_t async_tasks_group = dispatch_group_create(); 
        // update galley
        dispatch_group_async(async_tasks_group, async_tasks_queue, ^{
            [wself _updateGalleryAndVideos:^{} caller:caller];
        });
        // update manufacturer results
        dispatch_group_async(async_tasks_group, async_tasks_queue, ^{
            [wself _updateManufacturerResults:^{} caller:caller];
        });   
        // update driver results
        dispatch_group_async(async_tasks_group, async_tasks_queue, ^{
            [wself _updateDriverResults:^{} caller:caller];
        });
        // update stages
        dispatch_group_async(async_tasks_group, async_tasks_queue, ^{
            [wself _updateStages:^{} caller:caller];
        });  
        // update events and event entries
            dispatch_group_async(async_tasks_group, async_tasks_queue, ^{
                [wself _updateEvents:^{} caller:caller];
                [wself _updateEntries:^{} caller:caller];
            });
        dispatch_group_wait(async_tasks_group, DISPATCH_TIME_FOREVER);
        dispatch_release(async_tasks_group), async_tasks_group = NULL;
        dispatch_release(async_tasks_queue), async_tasks_queue = NULL; 
        // Fire completion block
        dispatch_async(caller, ^{
            NSLog(@"completed update");
            if (block) block();
        });
    });
}