NSURL problems in Swift

Question

I'm building a weather app and this whole block of code is an error. I've tried almost everything.

This is the code:

func getCurrentWeatherData() -> Void {
    let baseURL = NSURL(string: "https://api.forecast.io/forecast/\(apiKey)/")
    let forecastURL = NSURL(string: "37.8267,-122.423", relativeToURL: baseURL)

    let sharedSession = NSURLSession.sharedSession()
    let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(forecastURL!, completionHandler: { (location: NSURL!, response: NSURLResponse!, error: NSError!) -> Void in
      if (error == nil){
        let dataObject = NSData(contentsOfURL: location)
        let weatherDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataObject, options: nil, error: nil) as NSDictionary

        let currentWeather = Weather(weatherDictionary: weatherDictionary)

        dispatch_async(dispatch_get_main_queue(), { () -> Void in
          self.currentTemperature.text = "\(currentWeather.temperature)"
          self.iconView.image = currentWeather.icon!

          let formatter = NSDateFormatter()
          formatter.timeStyle = .ShortStyle
          self.currentTime.text = formatter.stringFromDate(NSDate())
          self.humidity.text = "\(Int(currentWeather.humidity * 100))%"
          self.rain.text = "\(Int(currentWeather.precipProbability))%"
          self.summary.text = "\(currentWeather.summary)"

          self.refreshActivityIndicator.stopAnimating()
          self.refreshActivityIndicator.hidden = true
          self.refreshButton.hidden = false
        })
      } else {
        let networkIssueController = UIAlertController(title: "Error", message: "Unable to load data. Connectivity error!", preferredStyle: .Alert)
        let okButton = UIAlertAction(title: "OK", style: .Default, handler: nil)
        networkIssueController.addAction(okButton)

        let cancelButton = UIAlertAction(title: "Cancel", style: .Cancel, handler: nil)
        networkIssueController.addAction(cancelButton)

        self.presentViewController(networkIssueController, animated: true, completion: nil)

        dispatch_async(dispatch_get_main_queue(), { () -> Void in
          self.refreshActivityIndicator.stopAnimating()
          self.refreshActivityIndicator.hidden = true
          self.refreshButton.hidden = false
        })
      }
    })
}

This is the error:

"/Users/Ethan/Downloads/Weather-master/Weather/ViewController.swift:39:117: '(NSURL!, NSURLResponse!, NSError!) -> Void' is not convertible to '(NSURL?, NSURLResponse?, NSError?) -> Void'"

Edit

Solve error above one...now the Code is: let weatherDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataObject, options: nil, error: nil) as NSDictionary

error is

/Users/Ethan/Downloads/Weather-master/Weather/ViewController.swift:42:85: Extra argument 'error' in call

Answer 1

change

   location: NSURL!, response: NSURLResponse!, error: NSError!  

to

   location: NSURL?, response: NSURLResponse?, error: NSError?  

if you are using swift2

   do {
        let jsonResult = try NSJSONSerialization.JSONObjectWithData(dataObject, options: NSJSONReadingOptions.MutableContainers) as? NSDictionary
   } catch let error as NSError {
         print(error)
   }