Reload data of UITableView in background

Question

In my app, I have a UITableViewController.

Its tableView is divided in 3 sections.

I download datas for each of those sections from my server. To do this, I have

Answer 1

The previous answers are absolutely right. However your implementation of reloadDatas & viewDidLoad is a bit problematic.

Just to clarify:

You want to complete the time consuming data loading stuff in a background thread, then update the UI/Cells when your data is ready on the main thread.

Like so:

  -(void)viewDidLoad
    {
       dispatch_queue_t concurrentQueue = dispatch_queue_create("com.my.backgroundQueue", NULL);
        dispatch_async(concurrentQueue, ^{
            [self reloadDatas];
        });
    }

-(void)reloadDatas
{
    // Expensive operations i.e pull data from server and add it to NSArray or NSDictionary
      [self f1];
      [self f2];
      [self f3];

    // Operation done - now let's update our table cells on the main thread  

    dispatch_queue_t mainThreadQueue = dispatch_get_main_queue();
    dispatch_async(mainThreadQueue, ^{

        [myDisplayedTable reloadData]; // Update table UI
    });
}