Slow Network - DidSelectRowAtIndexPath delayed

Question

I have a table that is refreshing itself every two seconds. It works great on the simulator and on my wifi. But once I switch to the cellular network (or any slow network), I cannot select the rows reliably.

Sometimes when I click a row it will work after 8 seconds. Sometimes never.

I thought my refresh function was causing the delay but I printed the time at the beginning and end of the function and it only takes 2 milliseconds.

Has anyone had a similar slow network issue? Any tips on what might be the cause of the hang-up?

My refresh function is called in viewDidLoad:

//Set timer to call refresh function every two seconds
[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(updateMethod) userInfo:nil repeats:YES];

My updateMethod is:

- (void) updateMethod
{
  [columnArray removeAllObjects];
  [self getColumnData];
  [homeTable reloadData];

}

getColumnData calls a website and puts data in the columnArray

Answer 1

You must not perform network operations on the main queue. You can create an NSOperationQueue to move the network logic to a background queue and only perform the UI update in the main queue when the network operation ends.

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
queue.name = @"Data request queue";

[queue addOperationWithBlock:^{
   [self getColumnData];
   [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        [homeTable reloadData];
    }];
 }];