Why cant I show my facebook interstitial ad after dismissing a view controller?

Question

Im working with ReplayKit and when I press the cancel or save button it dismisses the view controller and I would like to show an ad. The problem is that the ad doesn't show up and I get this error: How do I fix it? Thanks!

Warning: Exception caught during invocation of received message, dropping incoming message and invalidating the connection. Exception: This method must be called on the main thread

internal func previewControllerDidFinish(previewController: RPPreviewViewController) {

previewViewController.dismissViewControllerAnimated(true, completion: nil)

NSNotificationCenter.defaultCenter().postNotificationName("loadAd", object: nil)

}

Answer 1

All UI related operations must be done on the main thread. You could do something like this using GCD:

dispatch_async(dispatch_get_main_queue()) {
        previewViewController.dismissViewControllerAnimated(true, completion: nil)
}

You could also post the notification in the completion block of dismissViewControllerAnimated