JSON parsing error in Swift 2.0 - swift

Question

I'm learning to code in Swift 2.0 and I got stuck while compiling it into simulator. The self.setLabels(data!) line displays an info Thread 1: EXC_BAD_INSTRUCTION. Can anyone help me with this? I'm doing a trial-and-error technique but no luck yet...
lass ViewController: UIViewController {
#IBOutlet weak var cityNameTextField: UITextField!
#IBOutlet weak var cityNameLabel: UILabel!
#IBOutlet weak var cityTempLabel: UILabel!
#IBAction func getWeatherDataClick(sender: AnyObject) {
getWeatherData("http://api.openweathermap.org/data/2.5/weather?q=" + cityNameTextField.text! + "")
}
override func viewDidLoad() {
super.viewDidLoad()
getWeatherData("http://api.openweathermap.org/data/2.5/weather?q=London,uk&appid=2de143494c0b295cca9337e1e96b00e0")
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func getWeatherData(urlString: String) {
let url = NSURL(string: urlString)
let task = NSURLSession.sharedSession().dataTaskWithURL(url!) { (data, response, error) in
dispatch_async(dispatch_get_main_queue(), {
self.setLabels(data!)
})
}
task.resume()
}
func setLabels(weatherData: NSData) {
let jsonResult = AnyObject? ()
do {
if let jsonResult = try NSJSONSerialization.JSONObjectWithData(weatherData, options: []) as? NSDictionary {
print(jsonResult)
}
} catch {
print(error)
}
if let name = jsonResult!["name"] as? String {
cityNameLabel.text = name
}
if let main = jsonResult!["main"] as? NSDictionary {
if let temp = main["temp"] as? Double {
cityTempLabel.text = String(format: "%.1f", temp)
}
}
};
}

Answer 1

First guess would be: data == nil. Your function: setLabels: is not prepared to receive nil argument. Try to change declaration of this function to:
func setLabels(weatherData: NSData?)
Or even better handle data == nil possibility before calling setLabels, in your NSURLSession block:
if let weatherData = data as? NSData {
//your data is not nil
//you can securely call setLabels
self.setLabels(weatherData)
} else {
//ooops sth goes wrong your data is nil, try to figure out why
}