键入“MessagesController?”没有成员“setupNavBarWithUser”

嘿,伙计们,我已经在视图控制器文件中创建了我的自定义视图控制器,我正在尝试从另一个视图控制器调用它的函数。

fileprivate func registeruserintoDb(_ uid: String, values: [String: AnyObject]) {
        let ref = Database.database().reference()
        let usersReference = ref.child("users").child(uid)

        usersReference.updateChildValues(values, withCompletionBlock: { (err, ref) in

            if err != nil {
                print(err!)
                return

            }

            //            self.messagesController?.fetchUserAndSetupNavBarTitle()
            //            self.messagesController?.navigationItem.title = values["name"] as? String
            let user = User(dictionary: values)

            MessagesController?.setupNavBarWithUser(user)

            self.dismiss(animated: true, completion: nil)
        })
    }

}