ios - Can't I downcast inside a switch ? (Swift 3) -

i have 2 segues in same prepareforsegue, 1 connects uiviewcontroller subclass , other connects uicollectionviewcontroller subclass. i'm trying use switch/case polymorphism set destinationviewcontroller downcast inside switch not visible outside it, keeps seeing var uivc declared originally. doing wrong here ? error "value of type 'uiviewcontroller' has no member 'context'"

 let identifier: string!  var destinationtest: uiviewcontroller!      switch identifier {     case "add exercise":             destinationtest = segue.destination as! addexerciseviewcontroller     case "addexerciseincollectionview":             destinationtest = segue.destination as! addexercisecollectionvc     default:           break     }   destinationtest.context = self.context 

as rmaddy said, have declared destinationtest uiviewcontroller, though assigning specific uiviewcontroller subclasses inside switch, compiler knows destinationtest uiviewcontroller, can't access subclass properties via variable.

you either need 2 view controller subclasses inherit common superclass, defines context property , declare destinationtest of superclass, or use protocol provides context property:

property hascontext {     var context: context { set } }  class addexerciseviewcontroller: uiviewcontroller, hascontext {      var context: context      ... }  class addexercisecollectionvc: uiviewcontroller, hascontext {      var context: context      ... } 

then can say

let identifier: string! var destinationtest: hascontext!  switch identifier {     case "add exercise":             destinationtest = segue.destination as! hascontext     case "addexerciseincollectionview":             destinationtest = segue.destination as! hascontext     default:           break  }   destinationtest.context = self.context