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iOS Build a Weather App with Swift (Retired) Concurrency Writing Concurrent Networking Code

Posted by Ben Myhre
Ben Myhre
28,726 Points

MORE Nil value for response

I can hit the direct destination URL just fine and see the JSON data just fine. The original error I found was because the forecastURL was not unwrapped. It would not compile with a "value of optional type 'NSURL?' not unwrapped" I added the bang (forecastURL!) and and it would compile, but now when I run it, the response prints 'nil'. What is going on here?

import UIKit

class ViewController: UIViewController {

    private let apiKey = "MY_KEY"

    override func viewDidLoad() {
        super.viewDidLoad()
        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
            println(response)
        })
        downloadTask.resume()  
    }

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

}

2 Answers

Meek D
Meek D
3,457 Points
Meek D
Meek D
3,457 Points

If you don't receive any data I think you should do an "if let" to try to unwrapped the data, so your program will not crash. Hope that helps....

And also why you don't have any data into this line of code ?

private let apiKey = "MY_KEY"
Ben Myhre
Ben Myhre
28,726 Points

it is a private key. Sharing that on a public forum would be like punching myself in the face with hungry piranhas.

Art Hayes
Art Hayes
7,251 Points
Art Hayes
Art Hayes
7,251 Points

This happened to me as well - I had to 'Clean' xcode to get the error to go away.

class ViewController: UIViewController {

    private let apiKey = "xxxxxx"



    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)
        // here's the actual network call

        // here's our session object - and it's a singleton
        let sharedSession = NSURLSession.sharedSession()

        // create the task
        let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(forecastURL!, completionHandler: { (location: NSURL!, response: NSURLResponse!, error: NSError!) -> Void in

        println(location, response)

        })

        downloadTask.resume()

    }


}

I'll say this - after using Xcode heavily for the last few months - it is one buggy, temperamental beast.

Ben Myhre
Ben Myhre
28,726 Points

So... I finally got back to this issue and after a full reboot, it seems to work. I had tried the old "restart XCode" last time to no avail. A full reboot and time was the solution I guess. sigh.