ios - Why is my code crashing when I run it in Thread 6: NSOperationQueue? -

class viewcontroller: uiviewcontroller {      override func viewdidload() {         super.viewdidload()          let url = nsurl(string: "https://api.forecast.io/forecast/mykeyhere/")         let session = nsurlsession.sharedsession()         let task: nsurlsessiondownloadtask = session.downloadtaskwithurl(url!, completionhandler: { (location: nsurl!, response: nsurlresponse!, error: nserror!) -> void in             if error == nil {                 let data = nsdata(contentsofurl: location)                 let json: nsdictionary = nsjsonserialization.jsonobjectwithdata(data!, options: nil, error: nil) as! nsdictionary!                 println(json)             }         })         task.resume()      } 

this code download task weather api. wondering why getting error:

thread 6: exc_bad_instruction(code=exc_1386_invop, subcode=0x0).

thanks lot.

you're getting error because response not json (or json not dictionary). so, when parsing json, use optional binding gracefully handle nil or non-dictionary errors, perhaps examining body of response if fails, e.g.:

let task = session.downloadtaskwithurl(url!) { location, response, error in     if error == nil {         let data = nsdata(contentsofurl: location)         var error: nserror?         if let json = nsjsonserialization.jsonobjectwithdata(data!, options: nil, error: &error) as? nsdictionary {             println("json = \(json)")         } else {             println("error = \(error)")             let responsestring = nsstring(data: data!, encoding: nsutf8stringencoding)             println("not json; responsestring = \(responsestring)")             println(response)         }     } } task.resume() 

also, note, when using jsonobjectwithdata, not want gracefully check error, want use error parameter, too, noted above.

btw, make sure include latitude , longitude in url described in forecast.io api documentation, or else you'll non-json error response. if fix url avoid error, should still implement graceful handling of errors, above, or else app might crash whenever there server issues.