Passing data with segue through navigationController

Question

I'm trying to push data from one viewController to another. I've connected a viewController to another ViewController's navigationController and then set the identifier to "showItemSegue". I get an error in these two lines:

var detailController = segue.destinationViewController as ShowItemViewController detailController.currentId = nextId! 

Image illustration:

The code:

override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {       nextId = itemArray?.objectAtIndex(indexPath.row).objectForKey("objectId") as? NSString      self.performSegueWithIdentifier("showItemSegue", sender: self)  }   override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {      if (segue.identifier == "showItemSegue") {         var detailController = segue.destinationViewController as ShowItemViewController         detailController.currentId = nextId!     }  } 

Answer 1

The destination view controller of the segue is the UINavigationController. You need to ask it for its top view controller to get to the real destination view controller:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {     if segue.identifier == "showItemSegue" {         let navController = segue.destination as! UINavigationController         let detailController = navController.topViewController as! ShowItemViewController         detailController.currentId = nextId!     } }