добавить docvars в dfm из отдельных данных.

Другой пример:

func getJason(url: NSURL, completionHandler: (String?, NSError?) -> Void ) -> NSURLSessionTask {

    var finalData: String!
    let task = NSURLSession.sharedSession().dataTaskWithURL(url) { (data, response, error) -> Void in

        if error != nil{

            completionHandler(nil, error)
            return
        }
        else{

        if let urlContent = data{

            do{
                let jsonData = try NSJSONSerialization.JSONObjectWithData(urlContent, options: NSJSONReadingOptions.MutableContainers)

                if let ip = jsonData["ip"]{

                    finalData = ip as? String
                    completionHandler(finalData, nil)
                    return
                }

            }catch{
                print("EMPTY")
            }

        }

    }
}
    task.resume()
    return task
}

Затем я назвал его в viewDidLoad

getJason(url) { (ipAddress, error) -> Void in

        if error != nil{

            print(error)
        }
        else{
            if let ip = ipAddress{          //To get rid of optional

        self.ipLabelDisplay.text = "Your Ip Address is: \(ip)"

            }

        }
    }