Modern Collection Views

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var snapshot = NSDiffableDataSourceSnapshot<Section, Int>()
snapshot.appendSections([.main])
snapshot.appendItems(Array(0..<94))
dataSource.apply(snapshot, animatingDifferences: false)

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let cellRegistration = UICollectionView.CellRegistration<TextCell, Int> { (cell, indexPath, identifier) in
  // Populate the cell with our item description.
  cell.label.text = "\(identifier)"
}
dataSource = UICollectionViewDiffableDataSource<Section, Int>(
  collectionView: collectionView
) { (
  collectionView: UICollectionView,
  indexPath: IndexPath,
  identifier: Int
) -> UICollectionViewCell? in
  // Return the cell.
  return collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: identifier)
}

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let layout = UICollectionViewCompositionalLayout { (
  sectionIndex: Int,
  layoutEnvironment: NSCollectionLayoutEnvironment
  ) -> NSCollectionLayoutSection? in

  guard let sectionLayoutKind = SectionLayoutKind(rawValue: sectionIndex) else { return nil }
  let columns = sectionLayoutKind.columnCount

  // The group auto-calculates the actual item width to make
  // the requested number of columns fit, so this widthDimension is ignored.
  let itemSize = NSCollectionLayoutSize(
    widthDimension: .fractionalWidth(1.0),
    heightDimension: .fractionalHeight(1.0)
  )
  let item = NSCollectionLayoutItem(layoutSize: itemSize)
  item.contentInsets = NSDirectionalEdgeInsets(top: 2, leading: 2, bottom: 2, trailing: 2)

  let groupHeight = columns == 1 ?
    NSCollectionLayoutDimension.absolute(44) :
    NSCollectionLayoutDimension.fractionalWidth(0.2)
    // Element height takes 20% of section width
  let groupSize = NSCollectionLayoutSize(
    widthDimension: .fractionalWidth(1.0),
    heightDimension: groupHeight
  )
  let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitem: item, count: columns)

  let section = NSCollectionLayoutSection(group: group)
  section.contentInsets = NSDirectionalEdgeInsets(top: 20, leading: 20, bottom: 20, trailing: 20)
  section.contentInsetsReference = .readableContent
  return section
}