Can't pass data from UITableviewController into ViewController - keep getting Swift dynamic Cast Class Unconditional error

Question

I'm simply trying to pass core data that displays in a TableViewController to another ViewController - there seems to be something wrong with my prepareForSegueCode. Trying to pass the data and load it in viewDidLoad of the ViewController. Any help is so much appreciated - been working on this for hours with no luck.

TableViewController Code:

import UIKit
import CoreData

class MyEventsTableViewController: UITableViewController, NSFetchedResultsControllerDelegate {

var myEvents:[myEventsData] = []

var fetchResultController: NSFetchedResultsController!

func controllerWillChangeContent(controller: NSFetchedResultsController!) {
    tableView.beginUpdates()
}

func controller(controller: NSFetchedResultsController!, didChangeObject anObject: AnyObject!,atIndexPath indexPath: NSIndexPath!, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath!){

    switch type {
    case .Insert:
        tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
    case .Delete:
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
    case .Update:
    tableView.reloadRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)

    default:
        tableView.reloadData()
    }

    myEvents = controller.fetchedObjects as [myEventsData]

}

func controllerDidChangeContent(controller: NSFetchedResultsController) {
    tableView.endUpdates()
}

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    let cellIdentifier = "myEventsCell"
    let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as MyEventsTableViewCell

    let eventData = myEvents [indexPath.row]
    cell.eventNameLabel.text = "Name: " + eventData.eventName
    cell.startDateLabel.text = "Start: " + eventData.startDate
    cell.endDateLabel.text = "End: " + eventData.endDate

    cell.eventData = eventData

    cell.backgroundColor = UIColor.clearColor()



    return cell
}

override func prepareForSegue (segue: UIStoryboardSegue, sender: AnyObject!) {
    if segue.identifier == "showEventDetails" {
        if let indexPath = self.tableView.indexPathForSelectedRow() {

        let destinationController = segue.destinationViewController as MyEventDetailsViewController

        destinationController.eventData! = myEvents[indexPath.row]
        }
           }
}

DestinationViewController Code:

import UIKit

class MyEventDetailsViewController: UIViewController, UITableViewDelegate {


var eventData:myEventsData!


@IBOutlet weak var eventName: UILabel!
@IBOutlet weak var startDate: UILabel!
@IBOutlet weak var endDate: UILabel!
@IBOutlet weak var details: UILabel!
@IBOutlet weak var postComment: UIButton!
@IBOutlet weak var checkIn: UIButton!
@IBOutlet weak var addPhoto: UIButton!
@IBOutlet weak var myWineJournal: UIButton!


override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.

    self.eventName.text = eventData.eventName
    self.startDate.text = eventData.startDate
    self.endDate.text = eventData.endDate
    self.details.text = eventData.details

}

Answer 1

I see an error in this line:

destinationController.eventData! = myEvents[indexPath.row]

as you are using the forced unwrapping operator for assignment - that's not necessary as it should simply be:

destinationController.eventData = myEvents[indexPath.row]

Since the eventData property doesn't seem to be initialized, I'd expect a different exception though:

fatal error: unexpectedly found nil while unwrapping an Optional value

---

Addendum

The cast exception could be caused by this:

let destinationController = segue.destinationViewController as MyEventDetailsViewController

Are you sure you have set the custom class in IB for that view controller?

Update

As outlined in comments, it turns out the problem is that there's a navigation controller between the source and the destination view controller. The problem has been fixed as explained in this answer, consisting of retrieving the top view controller from the nav controller.