ios - How to call method of my ViewController from separate non UIViewController Class -

what im trying networkcall(asyncronous call) in seprate class file. when network call completed should throw function callback in actuall viewcontroller , update ui-views

i have facilitiesnewvc.swift class this

class facilitiesnewvc: uiviewcontroller, roomsdataprotocol {     var data = nsmutabledata()     var roomsdata = roomsdata()      override func viewdidload() {         super.viewdidload()         // additional setup after loading view.         //image background          roomsdata.startconnection();     }      // overriden method (not called)     func didfinishloadingurl(jsonresult:nsdictionary) -> void{         //this method not getting called         println("in view controller")     } } 

note: roomsdata.startconnection();

here roomsdata.swift

class roomsdata: nsobject, nsurlconnectiondelegate  {     var data = nsmutabledata()     var callback:roomsdataprotocol?      func startconnection(){         let urlpath: string = "http://blue.genetechz.com/qadir/bed_room.php"         var url: nsurl = nsurl(string: urlpath)!         var request: nsurlrequest = nsurlrequest(url: url)         var connection: nsurlconnection = nsurlconnection(request: request, delegate: self, startimmediately: false)!          println("startconnection");         connection.start()     }      func connection(connection: nsurlconnection!, didreceivedata data: nsdata!){          self.data.appenddata(data)          println("connection");     }      func connectiondidfinishloading(connection: nsurlconnection!) {         println("connectiondidfinishloading");          var err: nserror         var jsonresult: nsdictionary = nsjsonserialization.jsonobjectwithdata(data, options: nsjsonreadingoptions.mutablecontainers, error: nil) nsdictionary          callback?.didfinishloadingurl(jsonresult); // call overriden method in facilitiesnewvc          println("roomsdata")     } } 

and lastly here protocol i.e roomsdataprotocol

protocol roomsdataprotocol {     func didfinishloadingurl(jsondata:nsdictionary) } 

why overriden method in facilitiesnewvc.swift class (i.e didfinishloadingurl() ) not getting called?

in code posted, there no line sets callback variable in roomsdata class. ?. operator not call method in line

callback?.didfinishloadingurl(jsonresult); 

i suggest add

roomsdata.callback = self 

somewhere before calling

roomsdata.startconnection(); 

in facilitiesnewvc class.