title: Does NSURLConnection Block the Main/UI Thread
body: <p>I am downloading images in table view cells as they scroll onto the screen. For UX reasons, I start downloading the images in <code>- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath</code>.  I do not wait until the table view is done scrolling. When the table view cell is set, I start downloading images that I do not have already.  However, they do not seem to fully download until the table view stops moving.  As soon as it stops moving, the images almost download instantly.</p>
  
  <p>Is there anyway to use NSURLConnection where it is not blocked by the main UI thread? Or, is there a way where these images will download very quickly while the table view is being scrolled.</p>
  
  <p>** EDIT **</p>
  
  <p>To prove that NSURLConnection is slower I used NSThread to detach a new selector in a different thread.  I then download the data and call back to the main thread where I create a UIImage and show it in the table view.  This method works MUCH faster.</p>
  
  <p>Personally, I think that NSURLConnection is getting thrown into the event loop where the UITableView scrolling is blocking it.</p>