snapshot.swift

extension CollectionView {
    
    private func snapshotForCurrentState() -> NSDiffableDataSourceSnapshot<Section, Item> {
        
        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
        snapshot.appendSections(sections)
        for section in sections {
            snapshot.appendItems(items[section]!, toSection: section)
        }
        
        return snapshot
    }
}