UIAlertController+Popover.swift

  let alertController = UIAlertController(title: nil, message: "Alert message.", preferredStyle: .actionSheet)

  let defaultAction = UIAlertAction(title: "Default", style: .default, handler: { (alert: UIAlertAction!) -> Void in
    //  Do some action here.
  })

  let deleteAction = UIAlertAction(title: "Delete", style: .destructive, handler: { (alert: UIAlertAction!) -> Void in
    //  Do some destructive action here.
  })

  let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: { (alert: UIAlertAction!) -> Void in
    //  Do something here upon cancellation.
  })

  alertController.addAction(defaultAction)
  alertController.addAction(deleteAction)
  alertController.addAction(cancelAction)
  
  // 
  if let popoverController = alertController.popoverPresentationController {
    popoverController.sourceView = self.view
    popoverController.sourceRect = CGRect(x: self.view.bounds.midX, y: self.view.bounds.midY, width: 0, height: 0)
    popoverController.permittedArrowDirections = []
  }

  self.present(alertController, animated: true, completion: nil)