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iOS Build a Weather App with Swift (Retired) Concurrency Using Our JSON Data

Andrew Thompson
PLUS
Andrew Thompson
Courses Plus Student 1,796 Points
Posted by Andrew Thompson
Andrew Thompson
Courses Plus Student 1,796 Points

Having a problem with the newly updated Xcode 6 code in the teacher notes, still not working.

Here is my code:

        let baseURL = NSURL(string: "https://api.forecast.io/forecast/\(apiKey)/")
        let forecastURL = NSURL(string: "34.293413,-118.534371", 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()

        var urlContents = NSString(contentsOfURL: location, encoding: NSUTF8StringEncoding, error: nil)

        println(urlContents)

I get this error: Use of unresolved indentifier 'location'

2 Answers

Chris Shaw
Chris Shaw
26,676 Points
Chris Shaw
Chris Shaw
26,676 Points

Hi Andrew,

The urlContents assignment you have isn't needed since you're using sharedSession.downloadTaskWithURL which collects the result of the request in response, however to explain why you're getting an error that is because there is no variable called location in the current scope, that variable exists within the completionHandler closure therefore it's scoped to that part of the code and can't be used anywhere else.

If that is confusing I'm simply saying you don't need the below.

var urlContents = NSString(contentsOfURL: location, encoding: NSUTF8StringEncoding, error: nil)
println(urlContents)
Andrew Thompson
Andrew Thompson
Courses Plus Student 1,796 Points
Andrew Thompson
Andrew Thompson
Courses Plus Student 1,796 Points

Thank you for that, I realized he ended up deleting that, but then still added this code next:

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

        let dataObject = NSData(contentsOfURL: location)

Still giving me an error for 'location' being unresolved identifier.

The video he is clearly typing "location" for contentsofURL, and I've triple checked my code matches 100% to his.

Thank you!

Chris Shaw
Chris Shaw
26,676 Points
Chris Shaw
Chris Shaw
26,676 Points

As I said above location is scoped only to the closure so you need to execute your code within it, see the below.

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

    // This is redundant as response contains the same data
    let dataObject = NSData(contentsOfURL: location)
})

downloadTask.resume()
ch11
ch11
3,901 Points

The code from the tutorial is as follows:

        let sharedSession = NSURLSession.sharedSession()
        let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(forecastURL!, completionHandler: { (loacation: 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
            println(weatherDictionary)
            }
        })
        downloadTask.resume()
    }

After deleting the code 

let dataObject = NSData(contentsOfURL: location)

then, the following code gives an error: use of unresolved identifier 'dataObject'

            let weatherDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataObject, options: nil, error: nil) as NSDictionary

if I get rid of that code, there is no weatherDictionary to use in

            println(weatherDictionary)

I'm stuck :(