Question

I am trying to refresh a UITableView with new cells every 30 seconds. My array contains 30 elements, and for every new item I add to my array, I want to remove the last cell in my table. How can I go about doing this?

Answer 1

To refresh every 30 seconds, use an NSTimer.

NSTimer* timer = [NSTimer scheduledTimerWithTimeInterval:30
                           target:self selector:@selector(refreshTable)
                         userInfo:nil repeats:YES];

Add that new item in your -refreshTable. Make sure your dataSource and the table are in sync.

-(void)refreshTable {
   ...
   // modify the data source.
   [items removeLastObject];
   [items insertObject:newItem atIndex:0];

   // modify the table.
   [tableView beginUpdates];
   [tableView insertRowsAtIndexPaths:
      [NSArray arrayWithObject:[NSIndexPath indexPathForRow:0 inSection:0]]
                    withRowAnimation:withRowAnimation:UITableViewRowAnimationRight];
   [tableView deleteRowsAtIndexPaths:
      [NSArray arrayWithObject:[NSIndexPath indexPathForRow:29 inSection:0]]
                    withRowAnimation:UITableViewRowAnimationFade];
   [tableView endUpdates];
   ...
}

See the Table View Programming Guide for iPhone OS on how to perform batch insertion and deletion.