Using for loop to add to an array, objects aren't being added until for loop is completely done looping

Question

So, I am using the code below to cycle through json arrays if the json array returns positive, I add the json array to another array containing all of total arrays. This can take some time to complete however, because it is going through several different json urls plugging in different dynamic information.

I edited the code below to show more basic information. My problem is that data isnt actually entered into the array until the for loop is finished. I need it to be added as soon as it finds it, not after it runs through all the onlineChannels.count - Any help?

for (int i = 0; i<onlineChannels.count; i++) {
       [jsonResults addObject:[parsingJson objectAtIndex:0]];
        NSLog(@"%i",jsonResults.count);
        [MBProgressHUD hideAllHUDsForView:self.view animated:YES];
        [self.tableView reloadData];
    } else {
        [MBProgressHUD hideAllHUDsForView:self.view animated:YES];
        [self.tableView reloadData];
    }
}

Answer 1

My problem is that data isnt actually entered into the array until the for loop is finished.

How do you know?

I see that you're calling -reloadData, so perhaps you're expecting the change to be reflected in your table immediately? I believe that your objects are being added to the array immediately, but the change isn't displayed on the table right away. -reloadData doesn't actually redraw the table -- drawing happens as part of the main run loop. You're probably running this code on the main thread, and by doing so you're preventing the run loop from getting any time to redraw the table.

The best way to solve this sort of problem is to move time consuming processes like your loop to background threads. That will leave the main thread free to redraw the table as necessary, and it'll make your app more responsive as well.

Also, making the table reload all its data every time you add a single item even when that item's row isn't being displayed seems quite wasteful. Consider instead calling a method like reloadRowsAtIndexPaths:withRowAnimation: to update only the part of the table that has changed.