Hi i tried to code exactly as you say in the video but it gives an error when running it. NSURL? not unwrapped??

//Replace the string below with your API Key.
private let apiKey = "4de5319c1c8991a1ff2985013795b0b3"

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

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

    let weatherData = NSData.dataWithContentsOfURL(forecastURL, options: nil, error: nil)
    println(weatherData)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}