title: UITableViewCell accessoryView not appearing until much later
body: <p>I've got a UITableView with several entries. Upon selecting one, I need it to do a potentially time-consuming network operation. To give the user some feedback, I tried to place a UIActivityIndicatorView in the UITableViewCell. However, the spinner doesn't appear until much later -- after I've done the expensive operation! What am I doing wrong?</p>
  
  <pre><code>- (NSIndexPath *) tableView:(UITableView *) tableView
     willSelectRowAtIndexPath:(NSIndexPath *) indexPath {
  
    UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc]
                                         initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
  
    [spinner autorelease];
    [spinner startAnimating];
    [[tableView cellForRowAtIndexPath:indexPath] setAccessoryView:activity];
  
    if ([self lengthyNetworkRequest] == nil) {
      // ...
  
      return nil;
    }
  
    return indexPath;
  }
  </code></pre>
  
  <p>As you can see, I have the spinner being set to the accessoryView before the lengthy network operation. But it only appears after the <code>tableView:willSelectRowAtIndexPath:</code> method finishes.</p>