swift - prepareForSegue can't get the destination view controller on iOS 7 -

i have write ios app supports both ios 7 , 8 , in app have 2 view controllers , b navigation controllers , segue between them. when segue activates, have fetch data view controller view controller b. code works on ios 8 not on ios 7.

override func prepareforsegue(segue: uistoryboardsegue, sender: anyobject?) {     // new view controller using [segue destinationviewcontroller].     // pass selected object new view controller.      if segue.identifier == userdatasegue {         let navcontroller = segue.destinationviewcontroller as? uinavigationcontroller          if let userdatatableviewcontroller = navcontroller?.topviewcontroller as? userdatatableviewcontroller {             userdatatableviewcontroller.userdata = user         }     } } 

do know why happen , how can fix it? "work around" problem saving stuff in nsuserdefaults , reading in vc b make code mess.

i appreciate :d

don't forget create public property userdata in second viewcontroller.

override func prepareforsegue(segue: uistoryboardsegue!, sender: anyobject!)  { if (segue.identifier == "seguetest") { var svc = segue!.destinationviewcontroller secondviewcontroller;  svc.userdata = user  } }