swift - Got delegate nil error even it was set in the main viewcontroller -

i have simple app welcomevc shows greeting message person's name. in vc namevc, users can change name want called, , supposes update name on welcomevc when click back.

in order pass name namevc welcomevc, set protocol changenamedelegate in namevc, , created variable in class:

protocol changenamedelegate {     func updatename(name: string) } class nameviewcontroller: uiviewcontroller {     @iboutlet weak var nametextfield: uitextfield!     var changenamedelegate: changenamedelegate!     override func viewdidload() {      }      @ibaction func closenamevc(_ sender: uibutton) {         if let newname = nametextfield.text {             changenamedelegate.updatename(name: newname)         }          dismiss(animated: true, completion: nil)     }  } 

in welcomevc, have made sure register delegate , conforms protocol setting follows:

class welcomeviewcontroller: uiviewcontroller, uiviewcontrollertransitioningdelegate { let namevc = nameviewcontroller() override func viewdidload() {        namevc.changenamedelegate = self     } } extension welcomeviewcontroller: changenamedelegate {     func updatename(name: string) {         print("the name has been updated!")         namelabel.text = name     }  } 

however when ran app, got crash because changenamedelegate appeared nil. know missed there? in advance!

it seems instantiating new instance of nameviewcontroller when routing welcomeviewcontroller. should navigate namevc instantiated before.