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!
    }
}