MovieViewController.swift

movieDataSource = UICollectionViewDiffableDataSource<MovieSection, Movie>(collectionView: movieCollectionView, cellProvider: { (collectionView, indexPath, movie) -> UICollectionViewCell? in
         let movieSections = MovieSection.allCases[indexPath.section]
         switch movieSections {
         case .topRated:
            guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: TopRatedMovieCell.cellIdentifier, for: indexPath) as? TopRatedMovieCell else {
               return TopRatedMovieCell()
            }
            cell.movie = movie
            return cell
         case .onGoing:
            guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: OnGoingMovieCell.cellIdentifier, for: indexPath) as? OnGoingMovieCell else {
               return OnGoingMovieCell()
            }
            cell.movie = movie
            return cell
         case .upcoming:
            guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: UpcomingMovieCell.cellIdentifier, for: indexPath) as? UpcomingMovieCell else {
               return UpcomingMovieCell()
            }
            cell.movie = movie
            return cell
         case .popular:
            guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: PopularMovieCell.cellIdentifier, for: indexPath) as? PopularMovieCell else {
               return PopularMovieCell()
            }
            cell.movie = movie
            return cell
         }
      })
movieDataSource?.supplementaryViewProvider = {
         (collectionView, kind, indexPath) -> UICollectionReusableView? in
         guard let supplementaryView = collectionView.dequeueReusableSupplementaryView(
           ofKind: kind,
           withReuseIdentifier: HeaderView.reuseIdentifier,
           for: indexPath) as? HeaderView else { fatalError("Cannot create header view") }
         supplementaryView.label.text = MovieSection.allCases[indexPath.section].rawValue
         return supplementaryView
      }
movieDataSource?.apply(generateSnapshot(), animatingDifferences: false, completion: nil)