Could not Cast Value problems Swift iOS - ios

Question

I have an app where I ask the user to login first. After a successful login I want the username to follow to all the other view controllers in the app. I have tried declaring this as a public variable, but I am not sure how to do that properly (ie. it is not working in any instance) so I am now trying a prepareForSegue approach. However when I do i get a "Could not cast value of type 'SwiftLoginScreen.LoginVC' (0x10cdd33a0) to 'SwiftLoginScreen.ActionVC' (0x10cdd3130). (lldb)" - error.
I want to be able to call up the username from any and all view controllers in the app, but I am not able to solve this. I have the username from my HomeVC and I now want it to pass on to my ActionVC.
Home VC:
import UIKit
class HomeVC: UIViewController {
#IBOutlet var usernameLabel : UILabel!
var currentUser : NSString!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(true)
let prefs:NSUserDefaults = NSUserDefaults.standardUserDefaults()
let isLoggedIn:Int = prefs.integerForKey("ISLOGGEDIN") as Int
if (isLoggedIn != 1) {
self.performSegueWithIdentifier("goto_login", sender: self)
} else {
self.usernameLabel.text = prefs.valueForKey("USERNAME") as? String
currentUser = prefs.valueForKey("USERNAME") as? String
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let destinationVC = segue.destinationViewController as! ActionVC
destinationVC.operatingUser = self.currentUser;
}
#IBAction func gotoAction(sender : UIButton) {
let appDomain = NSBundle.mainBundle().bundleIdentifier
NSUserDefaults.standardUserDefaults().removePersistentDomainForName(appDomain!)
self.performSegueWithIdentifier("goto_action", sender: self)
}
}
Action VC:
import Foundation
import UIKit
class ActionVC : UIViewController, UIImagePickerControllerDelegate{
#IBOutlet var usernameLable : UILabel!
var operatingUser : NSString!
override func viewDidLoad() {
super.viewDidLoad()
self.usernameLable.text = operatingUser as? String
}

Answer 1

prepareForSegue will get called for all segues involving the View Controller. In your case it is being called for a segue where the destination view controller is an instance of LoginVC, but you have a forced downcast (as!) to ActionVC - so you get an exception at runtime.
You can use an optional binding to make sure that you are handling the correct segue -
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let destinationVC = segue.destinationViewController as? ActionVC {
destinationVC.operatingUser = self.currentUser;
}
}

Answer 2

Your problem can be solved by adding
a username variable in AppDelegate class.
If you have a variable named userName
in AppDelegate you can access it anywhere in your app without passing it.
class AppDelegate
{
var userName = "Admin"
}
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
In your first controller you can set
the value:
appDelegate.userName = "Value"
and use the same to access it from
another controller:
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
appDelegate.userName