swift - Error while getting Uber AccessToken in ios -

i trying accesstoken uberrides. followed uber developer portal tutorial. i'm not getting accesstoken loginmanager class while login. here code.

@ibaction func getride(sender: uibutton) {      let loginmanager = loginmanager()     loginmanager.login(requestedscopes:[.ridewidgets], presentingviewcontroller: self, completion: { accesstoken, error in         // completion block. if accesstoken non-nil, you’re go         print("::accesstoken::")         print(accesstoken)         print("::error::")         print(error)     })  } 

but i'm getting following log while clicking on custom button.

::accesstoken::
nil
::error::
optional(error domain=com.uber.rides-ios-sdk.ridesauthenticationerror code=20 "a network error occured." userinfo={nslocalizeddescription=a network error occured.})

i checked , internet connection working properly. still error occurring.
please me solve this.

also set callback uri uber developer dashboard

set start , end location params

  let pickuplocation = userlocation   let dropofflocation = tolocation   let params = rideparametersbuilder().setpickuplocation(pickuplocation).setdropofflocation(dropofflocation).build()     let loginmanager = loginmanager()    if tokenmanager.fetchtoken() != nil {         self.riderequestviewcontroller = riderequestviewcontroller(rideparameters: params, loginmanager: loginmanager)         self.riderequestviewcontroller.delegate = self         self.riderequestviewcontroller.view.frame = cgrectmake(0, 50, self.view.frame.size.width, self.view.frame.size.height - 50)         self.view.addsubview(self.riderequestviewcontroller.view)         self.addchildviewcontroller(self.riderequestviewcontroller)         self.riderequestviewcontroller.didmovetoparentviewcontroller(self)   }    else {          loginmanager.login(requestedscopes: [.ridewidgets], presentingviewcontroller: self) { (accesstoken, error) in             if error == nil {                 print(accesstoken)                 dispatch_async(dispatch_get_main_queue(), {                     tokenmanager.savetoken(accesstoken!)                     self.riderequestviewcontroller = riderequestviewcontroller(rideparameters: params, loginmanager:loginmanager)                     self.riderequestviewcontroller.delegate = self                     self.riderequestviewcontroller.view.frame = cgrectmake(0, 50, self.view.frame.size.width, self.view.frame.size.height - 50)                     self.view.addsubview(self.riderequestviewcontroller.view)                     self.addchildviewcontroller(self.riderequestviewcontroller)                     self.riderequestviewcontroller.didmovetoparentviewcontroller(self)                 })             }             else {                 dispatch_async(dispatch_get_main_queue(), {                     let alert = uialertcontroller(title: "error", message: error?.localizeddescription, preferredstyle:.alert)                      let action = uialertaction(title: "ok", style: .cancel, handler: nil)                      alert.addaction(action)                      self.presentviewcontroller(alert, animated: true, completion: nil)                 })             }         }      } 

set riderequestviewcontroller delegate , check if access token missing check callback uri in uber deshboard

  extension uberrideviewcontroller : riderequestviewcontrollerdelegate { func riderequestviewcontroller(riderequestviewcontroller: riderequestviewcontroller, didreceiveerror error: nserror)  {         let errortype = riderequestviewerrortype(rawvalue: error.code) ?? .unknown          switch errortype {         case .accesstokenmissing:            print("access missing")         // no accesstoken saved         case .accesstokenexpired:            print("expired")         // accesstoken expired / invalid         case .networkerror:            print("network error")        // network connectivity error        case .unknown:            print("error")        default:           print("default")       }    } }