NSUrl exc_bad_instruction? - swift

Question

I am trying to follow this tutorial and after some minor trial and error runs I have ran into a problem that I don't quite understand. I am receiving this error(?) exc_bad_instruction. I have read that it happens usually when you try to unwrap a nil or the nil isn't valid?
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath, object: PFObject?) -> PFTableViewCell? {
var cell:iGameTableViewCell? = tableView.dequeueReusableCellWithIdentifier(cellIdentifier) as? iGameTableViewCell
if(cell == nil) {
cell = NSBundle.mainBundle().loadNibNamed("iGameTableViewCell", owner: self, options: nil)[0] as? iGameTableViewCell
}
if let pfObject = object {
cell?.gameNameLabel?.text = pfObject["name"] as? String
var votes:Int? = pfObject["votes"] as? Int
if votes == nil {
votes = 0
}
cell?.gameVotesLabel?.text = "\(votes!) votes"
var credit:String? = pfObject["author"] as? String
if credit != nil {
cell?.gameCreditLabel?.text = "\(credit!)"
}
cell?.gameImageView?.image = nil
if var urlString:String? = pfObject["url"] as? String {
var url:NSURL? = NSURL(string: urlString!)
if var url:NSURL? = NSURL(string: urlString!) {
var error:NSError?
var request:NSURLRequest = NSURLRequest(URL: url!, cachePolicy: NSURLRequestCachePolicy.ReturnCacheDataElseLoad, timeoutInterval: 5.0)
NSOperationQueue.mainQueue().cancelAllOperations()
NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue(), completionHandler: {
(response:NSURLResponse!, imageData:NSData!, error:NSError!) -> Void in
cell?.gameImageView?.image = UIImage(data: imageData)
})
}
}
}
return cell
}

Answer 1

See these two lines:
var url:NSURL? = NSURL(string: urlString!)
if var url:NSURL? = NSURL(string: urlString!) {
First, you can't want them both; they both do the same thing in
different ways.
Second, the way the first line operates is dangerous. Delete it.
Third, delete the exclamation mark from urlString! and the type
declaration NSURL?.
Now you will just have this:
if var url = NSURL(string: urlString) {
And that is safe and is how such unwrapping should look.
EDIT: Just to clarify: This is a terribly self-defeating thing to do:
if var urlString:String? = pfObject["url"] as? String
Here's why. The if var ... = or if let ... = construct unwraps the Optional on the right side of the equal sign. That is its purpose: to unwrap the Optional, safely. But by adding the :String? declaration, you wrap it right back up again in an Optional, thus defeating the entire purpose of this construct! You want to say this:
if var urlString = pfObject["url"] as? String
Now urlString, if it is anything at all, is an unwrapped String, which is what you're after.