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iOS

Posted by Jonathan Carpenter
Jonathan Carpenter
10,251 Points

NSURL Optional in Weather App

I'm coding up a weather app along side Pasan in one of the iOS tracks. As far as I can tell my code matches his however I'm having a problem with my NSURL being an optional where his is not. Here is my code.

class ViewController: UIViewController {

    private let apiKey = "92a0b81218fc51a38a717d1aed2b4a22"

    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 sharedSession = NSURLSession.sharedSession()
        let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(forecastURL, completionHandler: {
            (NSURL!, NSURLResponse!, NSError!) -> Void in

        })

    }

It's returning forecastURL as an optional and then giving me an error in my download task constant because it says I need to unwrap forecastURL. I need help understanding whats going on here and how to fix it.

Thanks.

Jonathan Carpenter
Jonathan Carpenter
10,251 Points

Here is the code a bit further along following the video. 

class ViewController: UIViewController {

    private let apiKey = "92a0b81218fc51a38a717d1aed2b4a22"

    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 unwrappedForecastURL = forecastURL!

        let sharedSession = NSURLSession.sharedSession()
        let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(unwrappedForecastURL, completionHandler: {
            (location: NSURL!, response: NSURLResponse!, error: NSError!) -> Void in
                println(response)
        })
        downloadTask.resume()

    }

It's functioning properly. I just unwrapped forecastURL. I would still like to know why it was an optional in the first place.

2 Answers

Chris Shaw
Chris Shaw
26,676 Points

Hi Jonathan,

This isn't an issue with the course per say but an unforeseen update that took place in Xcode 6.1, as of 6.1 NSURL objects are now optionals so we can evaluate them properly through IF LET statements if the URL given couldn't be parsed whereas before this could have thrown an exception and caused a crash.

Jonathan Carpenter
Jonathan Carpenter
10,251 Points
Jonathan Carpenter
Jonathan Carpenter
10,251 Points

Wonderful, thanks.