HTTP GET request gets fatal error when network is disabled in iOS 9

Question

i have this simple HTTP GET request:

@IBAction func MyButton(sender: AnyObject) {
    let url = NSURL(string: "http://api.openweathermap.org/data/2.5/weather?q=Tehran,ir")
    let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in
        let datastring = NSString(data:data!, encoding:NSUTF8StringEncoding) as? String
        if error == nil {
        print("data is:")
        print(datastring)
        }else{
            if let err:String? = String(error?.description){
                print("faced to this error: \(err)")
            }
        }
    }
    task.resume()
}

when network is available data will be received correctly, but when i turn off WIFI and click on the button i face to this error:

fatal error: unexpectedly found nil while unwrapping an Optional value

how can i handle network error in my request? i use iOS 9 on iPod touch and Xcode 7 beta release 6, and i don't have developer program membership

Answer 1

You can use Reachability library to check for the internet connection. It is very easy to use.

UPDATE

You have to get your data after check for an error:

let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in
    if error == nil {
        let dataString = NSString(data:data!, encoding:NSUTF8StringEncoding) as? String
        println(dataString)
    } else {
        println(error)
    }
}