ios - Unwind Segue not being performed after shouldPerformSegueWithIdentifier UIAlertController -

i have unwind segue uiviewcontroller named detailviewcontroller mainviewcontroller defined (within mainviewcontroller):

@ibaction func deleteitemunwind(sender: uistoryboardsegue) {     let sourceviewcontroller = sender.sourceviewcontroller } 

in detailview, have button should perform segue connected scene exit name deleteitemunwindsegue, , in detailviewcontroller have prepareforsegue change value of variables. works fine. problem is, have following code in detailviewcontroller

    override func shouldperformseguewithidentifier(identifier: string!, sender: anyobject!) -> bool {      if (identifier == "deleteitemunwindsegue") {          let deleteitemalert: uialertcontroller = uialertcontroller(title: "delete item", message: "are sure want delete item?", preferredstyle: .actionsheet)          let cancelaction: uialertaction = uialertaction(title: "cancel", style: .cancel) { action -> void in             return false         }         deleteitemalert.addaction(cancelaction)          let deleteitemaction: uialertaction = uialertaction(title: "yes", style: .destructive) { action -> void in             return true         }         deleteitemalert.addaction(deletechoreaction)          self.presentviewcontroller(deleteitemalert, animated: true) {          }     }     return true } 

and while prepareforsegue code works, unwind segue itself not triggered dismiss view. ideas?

i figured out that(after reading on uialertcontroller) moment after alert displayed, code after carried out, wold automatically give false every time. able bypass creating generic first responder exit unwind segue, , have button item trigger segue.