I did the tests here, in this case also not to pass the delegate on, I think it's because of the "addSubview (horizontalController.view)" Regardless of impacts, I found this form more clean, I will adopt it in the next.

I used to use "closures" only in the return of asynchronous functions to "API", I had never thought to use for cases like this. I liked the idea, I made a little adaptation: override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) as! AppsGroupCell let appGroup = groups[indexPath.item] cell.titleLabel.text = appGroup.feed.title cell.horizontalController.appGroup = appGroup cell.horizontalController.collectionView.reloadData() cell.horizontalController.didSelectHandler = self.didSelectHandler return cell } fileprivate func didSelectHandler(feedResult:FeedResult){ let controller = AppDetailController() controller.navigationItem.title = feedResult.name navigationController?.pushViewController(controller, animated: true) }

Hi, direct assign "cell.horizontalController.didSelectHandler = self.didSelectHandler" will introduce a retain cycle Would suggest this, if you don't want your method cellForItemAt to be so much verbose cell.horizontalController.didSelectHandler = { [weak self] in result self?.didSelectHandler(feedResult: result){ }

Sorry, I meant didSelectItemAt

Ah okay. thank!

So in my AppsHorizontalController, that's where I have an ext for UIViewControllerDelegateFlowLayout because it didnt seem right putting this as an extension of the DataSource. So I have: var didSelectHandler: ((FeedResult) -> ())? override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) { if let app = dataSource.appGroup?.feed.results[indexPath.item] { didSelectHandler?(app) } } Then in my AppsPageDataSource, I have: var HandlerforNewVC: ((FeedResult) -> ())? func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! AppsGroupCell let appGroup = groups[indexPath.item] cell.titleLabel.text = appGroup.feed.title cell.horizontalController.dataSource.appGroup = appGroup cell.horizontalController.collectionView.reloadData() cell.horizontalController.didSelectHandler = { [weak self] feedResult in self?.HandlerforNewVC?(feedResult) } return cell } Then in AppsPageController, I have: let dataSource = AppsPageDataSource() override func viewDidLoad() { super.viewDidLoad() dataSource.HandlerforNewVC = { [weak self] feedResult in let controller = AppDetailController(appId: feedResult.id) controller.navigationItem.title = feedResult.name self?.navigationController?.pushViewController(controller, animated: true) } } I got it working but I don't know if this is the right way to do it. Would appreciate your advice on this. Thank you!