3D Touch Preview Interaction

    override var previewActionItems: [UIPreviewActionItem] {
        get {
            let uncheck = UIPreviewAction(title: "Uncheck", style: .default) { (_, viewController : UIViewController) in
                if let vc = viewController as? OptionsViewController, let item = vc.item {
                    vc.delegate?.optionsDid(uncheck: item)
                }
            }

            let delete = UIPreviewAction(title: "Delete", style: .destructive) { (_, viewController : UIViewController) in
                if let vc = viewController as? OptionsViewController, let item = vc.item {
                    vc.delegate?.optionsDid(delete: item)
                }
            }

            return [uncheck, delete]
        }
    }

    var previewInteraction : UIPreviewInteraction?

    override func viewDidLoad() {
        super.viewDidLoad()

        registerForPreviewing(with: self, sourceView: tableView)

        previewInteraction = UIPreviewInteraction(view: tableView)
        previewInteraction?.delegate = self
    }

    func previewInteraction(_ previewInteraction: UIPreviewInteraction, didUpdatePreviewTransition transitionProgress: CGFloat, ended: Bool) {
        presentedOptionsController?.updateUI(for: previewInteraction)
    }

    func previewInteractionDidCancel(_ previewInteraction: UIPreviewInteraction) {
        presentedOptionsController?.commitAction()
        presentedOptionsController = nil
    }

    optional func previewInteractionShouldBegin(_ previewInteraction: UIPreviewInteraction) -> Bool {
        return true
    }

    optional func previewInteraction(_ previewInteraction: UIPreviewInteraction, didUpdateCommitTransition transitionProgress: CGFloat, ended: Bool) {
        presentedOptionsController?.updateUI(for: previewInteraction)

        if ended {
            presentedOptionsController?.finishedPreviewing()
        }
    }