FHDiffableCollectionViewController

Author: FelixHerrmann

Sources/FHDiffableViewControllers/FHDiffableCollectionViewController.swift

@@ -0,0 +1,206 @@
+#if !os(macOS)
+
+import UIKit
+
+/// A subclass of **UICollectionViewController** with diffable data source.
+open class FHDiffableCollectionViewController<SectionIdentifierType, ItemIdentifierType>: UICollectionViewController where SectionIdentifierType: Hashable, ItemIdentifierType: Hashable {
+    
+    // MARK: - Enums
+    
+    /// The type of layout you want to initialize your collection view with.
+    public enum LayoutType {
+        
+        /// Creates  a default **UICollectionViewCompositionalLayout**. This is intended to be used for test purposes.
+        case `default`
+        
+        /// Use a **UICollectionViewFlowLayout**.
+        case flow(UICollectionViewFlowLayout)
+        
+        /// Use a **UICollectionViewCompositionalLayout**.
+        case compositional(UICollectionViewCompositionalLayout)
+        
+        /// Use your custom **UICollectionViewLayout**.
+        case custom(UICollectionViewLayout)
+        
+    }
+    
+    
+    // MARK: - Typealias
+    
+    /// A typealias for **UICollectionViewDiffableDataSource** type.
+    public typealias FHDataSource = UICollectionViewDiffableDataSource<SectionIdentifierType, ItemIdentifierType>
+    
+    /// A typealias for **NSDiffableDataSourceSnapshot** type.
+    public typealias FHSnapshot = NSDiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>
+    
+    /// A typealias for **FHDiffableDataSourceSnapshotSection** array type.
+    public typealias FHSnapshotData = [FHDiffableDataSourceSnapshotSection<SectionIdentifierType, ItemIdentifierType>]
+    
+    
+    // MARK: - Initializers
+    
+    /// Initializes a **FHDiffableCollectionViewController** and configures the collection view with the provided layout.
+    ///
+    /// - Parameters:
+    ///     - layoutType: The type of layout the collection view should use.
+    ///
+    /// - Returns: An initialized **FHDiffableCollectionViewController** object.
+    public init(layout layoutType: LayoutType = .default) {
+        switch layoutType {
+        case .default:
+            let item = NSCollectionLayoutItem(layoutSize: .init(widthDimension: .fractionalWidth(1/3), heightDimension: .fractionalWidth(1/3)))
+            item.contentInsets = NSDirectionalEdgeInsets(top: 8, leading: 8, bottom: 8, trailing: 8)
+            let group = NSCollectionLayoutGroup.horizontal(layoutSize: .init(widthDimension: .fractionalWidth(1), heightDimension: .estimated(0)), subitems: [item])
+            group.contentInsets = NSDirectionalEdgeInsets(top: 8, leading: 8, bottom: 8, trailing: 8)
+            let section = NSCollectionLayoutSection(group: group)
+            let headerItem = NSCollectionLayoutBoundarySupplementaryItem(layoutSize: .init(widthDimension: .fractionalWidth(1), heightDimension: .estimated(32)), elementKind: UICollectionView.elementKindSectionHeader, alignment: .top)
+            headerItem.pinToVisibleBounds = true
+            section.boundarySupplementaryItems = [headerItem]
+            let compositionalLayout = UICollectionViewCompositionalLayout(section: section)
+            super.init(collectionViewLayout: compositionalLayout)
+        case .flow(let flowLayout):
+            super.init(collectionViewLayout: flowLayout)
+        case .compositional(let compositionalLayout):
+            super.init(collectionViewLayout: compositionalLayout)
+        case .custom(let layout):
+            super.init(collectionViewLayout: layout)
+        }
+    }
+    
+    required public init?(coder: NSCoder) {
+        super.init(coder: coder)
+    }
+    
+    
+    // MARK: - Private Properties
+    
+    private var _cellProvider: FHDataSource.CellProvider = { (collectionView, indexPath, itemIdentifier) in
+        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "defaultCell", for: indexPath)
+        cell.backgroundColor = .systemTeal
+        cell.layer.cornerRadius = 8
+        return cell
+    }
+    
+    private var _supplementaryViewProvider: FHDataSource.SupplementaryViewProvider = { (collectionView, kind, indexPath) in
+        let reuseableHeaderView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "defaultHeader", for: indexPath)
+        reuseableHeaderView.backgroundColor = .systemIndigo
+        return reuseableHeaderView
+    }
+    
+    private lazy var _dataSource: FHDataSource = {
+        let dataSource = FHDataSource(collectionView: collectionView, cellProvider: cellProvider)
+        dataSource.supplementaryViewProvider = supplementaryViewProvider
+        return dataSource
+    }()
+    
+    
+    // MARK: - Public Properties
+    
+    /// The cell provider which creates the cells.
+    ///
+    /// Override this property to configure a custom cell.
+    ///
+    /// The default implementation just shows an empty cell.
+    ///
+    ///     override var cellProvider: UICollectionViewDiffableDataSource<SectionIdentifierType, ItemIdentifierType>.CellProvider {
+    ///         return { (collectionView, indexPath, itemIdentifier) in
+    ///             let cell = collectionView.dequeueReusableCell(withIdentifier: /*your identifier*/, for: indexPath) as? CustomCell
+    ///             /*customize your cell here*/
+    ///             return cell
+    ///         }
+    ///     }
+    ///
+    /// - important: Do not forget to register the reuseable cell before the first snapshot is applied!
+    ///
+    ///       collectionView.register(CustomCell.self, forCellReuseIdentifier: /*your identifier*/) // e.g. in viewDidLoad()
+    open var cellProvider: UICollectionViewDiffableDataSource<SectionIdentifierType, ItemIdentifierType>.CellProvider {
+        return _cellProvider
+    }
+    
+    /// The supplementary view provider which creates the supplementary views.
+    ///
+    /// Override this property to configure a custom supplementary view.
+    ///
+    /// The default implementation just shows an empty section header.
+    ///
+    ///     override var supplementaryViewProvider: UICollectionViewDiffableDataSource<SectionIdentifierType, ItemIdentifierType>.SupplementaryViewProvider {
+    ///         return { (collectionView, kind, indexPath) in
+    ///             let supplementaryView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: /*your identifier*/, for: indexPath) as? CustomReuseableView
+    ///             /*customize your supplementary view here*/
+    ///             return supplementaryView
+    ///         }
+    ///     }
+    ///
+    /// - important: Do not forget to register the reuseable view before the first snapshot is applied!
+    ///
+    ///       collectionView.register(CustomReuseableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: /*your identifier*/) // e.g. in viewDidLoad()
+    open var supplementaryViewProvider: UICollectionViewDiffableDataSource<SectionIdentifierType, ItemIdentifierType>.SupplementaryViewProvider {
+        return _supplementaryViewProvider
+    }
+    
+    /// The data source for the collection view.
+    ///
+    /// Override this property only if a custom **UICollectionViewDiffableDataSource** should be applied.
+    /// For cell configuration overried the `cellProvider` property.
+    /// For supplementary view configuration override the `supplementaryViewProvider` property.
+    ///
+    ///     lazy var customDataSource: CustomDataSource = {
+    ///         let dataSource = CustomDataSource(collectionView: collectionView, cellProvider: cellProvider)
+    ///         dataSource.supplementaryViewProvider = supplementaryViewProvider
+    ///         return dataSource
+    ///     }()
+    ///
+    ///     override var dataSource: UICollectionViewDiffableDataSource<SectionIdentifierType, ItemIdentifierType> {
+    ///         return customDataSource
+    ///     }
+    ///
+    /// - important: You need to use a lazy var for it to work properly!
+    open var dataSource: UICollectionViewDiffableDataSource<SectionIdentifierType, ItemIdentifierType> {
+        return _dataSource
+    }
+    
+    
+    // MARK: - Public Methods
+    
+    /// This method applys a new snapshot to the collection view.
+    ///
+    /// This is the equivalent for `reloadData()` or `performBatchUpdates(_:)`
+    ///
+    /// With the `animatingDifferences`parameter the update animation can be disabled.
+    ///
+    /// If you do not want to use **FHSnapshotData** you can write your own `applySnapshot()` method like that:
+    ///
+    ///     func applySnapshot() {
+    ///         var snapshot = FHSnapshot()
+    ///         snapshot.appendSections([/*your sections*/])
+    ///         snapshot.appendItems([/*your items*/], toSection: /*your section*/) // do that for every section
+    ///         dataSource.apply(snapshot, animatingDifferences: true, completion: nil)
+    ///     }
+    ///
+    /// - Parameters:
+    ///   - snapshotData: The data snapshot for the collection view.
+    ///   - animatingDifferences: A boolean value to deactive the animation. Default value is `true`.
+    ///   - completion: The completion block for when the update is finished. Default value is `nil`.
+    open func applySnapshot(_ snapshotData: FHSnapshotData, animatingDifferences: Bool = true, completion: (() -> Void)? = nil) {
+        var snapshot = FHSnapshot()
+        
+        snapshot.appendSections(snapshotData.map({ $0.sectionIdentifier }))
+        snapshotData.forEach { (section) in
+            snapshot.appendItems(section.itemIdentifiers, toSection: section.sectionIdentifier)
+        }
+        
+        dataSource.apply(snapshot, animatingDifferences: animatingDifferences, completion: completion)
+    }
+    
+    
+    // MARK: - Overrides
+    
+    open override func viewDidLoad() {
+        super.viewDidLoad()
+        
+        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "defaultCell")
+        collectionView.register(UICollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "defaultHeader")
+    }
+}
+
+#endif