fixed SupplimentoryView private issue and added SupplimentoryView to multisession example demo

Author: suhitp

GenericDataSource/Cells/HeaderFooterReusableView.swift

@@ -7,13 +7,13 @@
 
 import UIKit
 
-class HeaderFooterReusableView: UICollectionReusableView {
+class HeaderFooterReusableView: UICollectionReusableView, NibReusable {
 
     @IBOutlet var headerLabel: UILabel!
 
     override func awakeFromNib() {
         super.awakeFromNib()
-        // Initialization code
+        backgroundColor = .lightGray
     }
 
     func render(with header: String) {

GenericDataSource/Cells/HeaderFooterReusableView.xib

@@ -10,7 +10,7 @@
     <objects>
         <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner"/>
         <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
-        <collectionReusableView opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" id="U6b-Vx-4bR">
+        <collectionReusableView opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" id="U6b-Vx-4bR" customClass="HeaderFooterReusableView" customModule="GenericDataSource" customModuleProvider="target">
             <rect key="frame" x="0.0" y="0.0" width="320" height="50"/>
             <autoresizingMask key="autoresizingMask"/>
             <subviews>
@@ -27,6 +27,9 @@
                 <constraint firstItem="1r3-Wd-C5y" firstAttribute="centerY" secondItem="U6b-Vx-4bR" secondAttribute="centerY" id="NKu-kK-xHS"/>
                 <constraint firstAttribute="trailing" secondItem="1r3-Wd-C5y" secondAttribute="trailing" constant="20" symbolic="YES" id="pUZ-b0-hZS"/>
             </constraints>
+            <connections>
+                <outlet property="headerLabel" destination="1r3-Wd-C5y" id="fP1-5G-OHG"/>
+            </connections>
             <point key="canvasLocation" x="139" y="129"/>
         </collectionReusableView>
     </objects>

GenericDataSource/DataSource/CollectionDiffableDataSource/DiffableCollectionViewDataSource.swift

@@ -27,7 +27,8 @@ open class DiffableCollectionViewDataSource<Section: SectionType, Item>: NSObjec
     private var sections: [CellSection] = []
     private weak var collectionView: UICollectionView?
     private var cellProvider: (UICollectionView, IndexPath, Item) -> UICollectionViewCell?
-    private var supplementaryViewProvider: DiffableCollectionViewDataSource<Section, Item>.SupplementaryViewProvider?
+   
+    public var supplementaryViewProvider: DiffableCollectionViewDataSource<Section, Item>.SupplementaryViewProvider?
 
     // MARK: init
 

GenericDataSource/Extensions/Reusable+Extensions.swift

@@ -63,7 +63,7 @@ public extension UICollectionView {
 
 
     //MARK: UICollectionReusableView
-    final func register<T: UICollectionReusableView>(supplementaryViewType: T.Type, ofKind elementKind: String)
+    final func register<T: UICollectionReusableView>(_ supplementaryViewType: T.Type, ofKind elementKind: String)
         where T: NibReusable {
             self.register(
                 supplementaryViewType.nib,
@@ -72,7 +72,7 @@ public extension UICollectionView {
             )
     }
 
-    final func register<T: UICollectionReusableView>(supplementaryViewType: T.Type, ofKind elementKind: String)
+    final func register<T: UICollectionReusableView>(_ supplementaryViewType: T.Type, ofKind elementKind: String)
         where T: Reusable {
             self.register(
                 supplementaryViewType.self,

GenericDataSource/ViewController/MultiSection/MultiSectionCollectionViewController.swift

@@ -45,57 +45,29 @@ class MultiSectionCollectionViewController: UICollectionViewController {
     required init?(coder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
-
-    fileprivate func configureDataSource() {
-       
-        dataSource = DiffableCollectionViewDataSource<Section, AnyDifferentiable>(
-            collectionView: collectionView,
-            cellProvider: { (collectionView, indexPath, anyDifferentiable) -> UICollectionViewCell? in
-                let section: CellSection = self.dataInput[indexPath.section].model
-                switch section {
-                case .vertical:
-                    let cell = collectionView.dequeueReusableCell(for: indexPath) as VerticalCell
-                    if let carousel = anyDifferentiable.base as? Carousel {
-                        cell.render(with: carousel)
-                    }
-                    return cell
-                case .horizontal:
-                    let cell = collectionView.dequeueReusableCell(for: indexPath) as HorizontalCell
-                    if let playlist = anyDifferentiable.base as? Playlist {
-                        cell.render(with: playlist)
-                    }
-                    return cell
-                case .customText:
-                    let cell = collectionView.dequeueReusableCell(for: indexPath) as CustomTextCell
-                    if let ads = anyDifferentiable.base as? Ads {
-                        cell.render(with: ads)
-                    }
-                    return cell
-                }
-            }
-        )
-        
-        let reusableView = 
-    }
-
+    
     override func viewDidLoad() {
         super.viewDidLoad()
 
-        collectionView.backgroundColor = .systemBackground
-        navigationItem.title = "MultiSection Demo"
-        collectionView.delegate = self
-        
+        setupViews()
         setupBarButtons()
         registerCells()
         configureDataSource()
         setupData()
     }
 
+    private func setupViews() {
+        collectionView.backgroundColor = .systemBackground
+        navigationItem.title = "MultiSection Demo"
+        collectionView.delegate = self
+    }
+    
     private func registerCells() {
         // Register cell classes
         collectionView.register(VerticalCell.self)
         collectionView.register(HorizontalCell.self)
         collectionView.register(CustomTextCell.self)
+        collectionView.register(HeaderFooterReusableView.self, ofKind: UICollectionView.elementKindSectionHeader)
     }
 
     private func setupData() {
@@ -131,6 +103,47 @@ class MultiSectionCollectionViewController: UICollectionViewController {
         }
     }
 
+    // MARK: DiffableCollectionViewDataSource
+    
+    fileprivate func configureDataSource() {
+       
+        dataSource = DiffableCollectionViewDataSource<Section, AnyDifferentiable>(
+            collectionView: collectionView,
+            cellProvider: { (collectionView, indexPath, anyDifferentiable) -> UICollectionViewCell? in
+                let section: CellSection = self.dataInput[indexPath.section].model
+                switch section {
+                case .vertical:
+                    let cell = collectionView.dequeueReusableCell(for: indexPath) as VerticalCell
+                    if let carousel = anyDifferentiable.base as? Carousel {
+                        cell.render(with: carousel)
+                    }
+                    return cell
+                case .horizontal:
+                    let cell = collectionView.dequeueReusableCell(for: indexPath) as HorizontalCell
+                    if let playlist = anyDifferentiable.base as? Playlist {
+                        cell.render(with: playlist)
+                    }
+                    return cell
+                case .customText:
+                    let cell = collectionView.dequeueReusableCell(for: indexPath) as CustomTextCell
+                    if let ads = anyDifferentiable.base as? Ads {
+                        cell.render(with: ads)
+                    }
+                    return cell
+                }
+            }
+        )
+        
+        dataSource.supplementaryViewProvider = { (collectionView, kind, indexPath) in
+            guard indexPath.section > 0 else {
+                return nil
+            }
+            let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, for: indexPath) as HeaderFooterReusableView
+            headerView.render(with: "HeaderTitle: Section-\(indexPath.section)")
+            return headerView
+        }
+    }
+    
     // MARK: Private methods
 
     fileprivate func setupBarButtons() {
@@ -191,4 +204,12 @@ extension MultiSectionCollectionViewController: UICollectionViewDelegateFlowLayo
             return CGSize(width: view.frame.width, height: 98)
         }
     }
+    
+    func collectionView(_ collectionView: UICollectionView,
+                          layout collectionViewLayout: UICollectionViewLayout,
+                          referenceSizeForHeaderInSection section: Int) -> CGSize {
+        guard section > 0 else { return .zero }
+        return CGSize(width: UIScreen.main.bounds.width, height: 50)
+    }
+
 }