Swift - How to get OpenWeatherMap JSON Data?

Question

The following app should get the user's current location and then display the Name and Temperature of that location using OpenWeatherMap.

import UIKit
import CoreLocation

class ViewController: UIViewController, CLLocationManagerDelegate {

    @IBOutlet weak var location: UILabel!
    @IBOutlet weak var temperature: UILabel!

    var locationManager: CLLocationManager = CLLocationManager()
    var startLocation: CLLocation!

    func extractData(weatherData: NSData) {
        let json = try? NSJSONSerialization.JSONObjectWithData(weatherData, options: []) as! NSDictionary

        if json != nil {
            if let name = json!["name"] as? String {
                location.text = name
            }

            if let main = json!["main"] as? NSDictionary {
                if let temp = main["temp"] as? Double {
                    temperature.text = String(format: "%.0f", temp)
                }
            }
        }
    }

    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        let latestLocation: AnyObject = locations[locations.count - 1]

        let lat = latestLocation.coordinate.latitude
        let lon = latestLocation.coordinate.longitude

        // Put together a URL With lat and lon
        let path = "http://api.openweathermap.org/data/2.5/weather?lat=\(lat)&lon=\(lon)&appid=2854c5771899ff92cd962dd7ad58e7b0"
        print(path)            

        let url = NSURL(string: path)

        let task = NSURLSession.sharedSession().dataTaskWithURL(url!) { (data, response, error) in
            dispatch_async(dispatch_get_main_queue(), {
                self.extractData(data!)
            })
        }

        task.resume()
    }

    func locationManager(manager: CLLocationManager,
        didFailWithError error: NSError) {

    }

    override func viewDidLoad() {
        super.viewDidLoad()

        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.delegate = self
        locationManager.requestWhenInUseAuthorization()
        locationManager.startUpdatingLocation()
        startLocation = nil
    }
}

I've been learning how to get data from OpenWeatherMap following this tutorial: https://www.youtube.com/watch?v=r-LZs0De7_U

The app crashes at:

self.extractData(data!)

as data is equal to nil, this shouldn't be happening as when I copy and paste the printed path into my web browser, the data is there. I'm sure I've followed the tutorial correctly, so what's the problem and how do I fix it?

**As always:** If an API provides an `error` parameter **first** check that parameter and handle the error. In case of `dataTaskWithURL` if an error occurs, `data` is `nil`, if there is no error, `error` is `nil` and `data` is valid. **NEVER EVER** forced unwrap optionals when receiving data from the network. — vadian, Mar 02 '16 at 17:47
I understand that, but in this situation, why am I not getting the data in the first place. — simpleguy, Mar 02 '16 at 17:52
Once again: Handle the error, I guess it's an ATS (App Transport Security) issue. — vadian, Mar 02 '16 at 17:54
@vadian I shoudn't have to as this shouldn't normally happen. Skip to 16:34 of the video, my code is the same bar a few changes due to swift updates. Why does it work for him but not me? — simpleguy, Mar 02 '16 at 18:00
You seem to be immune to suggestions: What error do you get? — vadian, Mar 02 '16 at 18:02
as shown in the start of video demo uses xcode 6.2, which will have iOS 8.2, the ATS has come with iOS 9/xcode 7. so if you try it with the latest xcode/device you need to add ATS additionally than the video instructions — HardikDG, Mar 02 '16 at 18:05

score 3 · Accepted Answer · edited May 23 '17 at 12:16

3

The problem is with Transport Security - which causes issues for lots of us. Here's one of the SO answers explaining how to resolve it Transport security has blocked a cleartext HTTP

If you make the setting in your plist - set the NSAllowsArbitraryLoads key to YES under NSAppTransportSecurity dictionary in your .plist file - then it works.

edited May 23 '17 at 12:16

Community

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answered Mar 02 '16 at 17:57

Russell

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Swift - How to get OpenWeatherMap JSON Data?

1 Answers1