Swift中的NSURL问题

我正在构建一个天气应用程序，这整段代码都是错误的 . 我几乎尝试了一切 .

这是代码：

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
        })
      }
    })
}

这是错误：

“/ Users /Ethan/Downloads/Weather-master/Weather/ViewController.swift:39:117：'（NSURL！，NSURLResponse！，NSError！） - > Void'不能转换为'（NSURL？，NSURLResponse？， NSError？） - > Void'“

Edit

解决错误高于一...现在代码是：let weatherDictionary：NSDictionary = NSJSONSerialization.JSONObjectWithData（dataObject，options：nil，error：nil）as NSDictionary

错误是

/Users/Ethan/Downloads/Weather-master/Weather/ViewController.swift:42:85：通话中的额外参数'错误'