iOS UIImageView not refreshing automatically

Question

I'm learning iOS programming by following this wonderful tutorial, except I'm targeting iOS 9 and make some small modifications.

In the tableView() function below, I can get thumbnail image downloaded and my handlers invoked, as evident from the console print out of the two logging lines. However, when the app is running (in simulator), I have to click on each table cell to get the image to show up. I tried to see if there is a refresh() or something like that in the UIImageView or the table cell, but found nothing.

How to make the image show up immediately as the data is received?

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell: UITableViewCell = tableView.dequeueReusableCellWithIdentifier(kCellIdentifier)!
    let album = self.albums[indexPath.row]

    // ... setting up other cell's data, see the tutorial link

    // Start by setting the cell's image to a static file
    // Without this, we will end up without an image view!
    cell.imageView?.image = UIImage(named: "Blank52")

    let request: NSURLRequest = NSURLRequest(URL: thumbnailURL)
    let urlSession = NSURLSession.sharedSession()
    urlSession.dataTaskWithRequest(request, completionHandler: {(data, response, error) -> Void in
        print("received thumbnail \(thumbnailURLString)") // reached
        if error == nil {
            // Convert the downloaded data in to a UIImage object
            let image = UIImage(data: data!)
            // Update the cell
            dispatch_async(dispatch_get_main_queue(), {
                print("...dispatched thumbnail image for \(thumbnailURLString)") // reached
                if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) {
                    cellToUpdate.imageView?.image = image
                }
            })
        }
    }).resume()

    return cell
}

Answer 1

I figured out a work around. If I also update the text slight, the image shows up right the way without clicking on the table view cell.

cellToUpdate.imageView?.image = image
cellToUpdate.textLabel?.text = "\(album.title) " // a space is added to the end to make a difference and force the cell to be updated

Sounds like a bug in UITableViewCell (or the simulator? haven't tried on a real device) to me.