[Examples] CustomCollectionView in Swift3 (#2591)

* new Swift example

* removed asyncDataSource and asyncDelegate. Also using collectionNode methods instead of collectionView

* Fixing the folder structure

* Updated with @george-gw feedback. Thanks George.

examples/CustomCollectionView-Swift/Sample/ViewController.swift

@@ -0,0 +1,101 @@
+//
+//  ViewController.swift
+//  Sample
+//
+//  Created by Rajeev Gupta on 11/9/16.
+//
+//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+//  FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+//  ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+//  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+import UIKit
+import AsyncDisplayKit
+
+class ViewController: UIViewController, MosaicCollectionViewLayoutDelegate, ASCollectionDataSource, ASCollectionDelegate {
+  
+  var _sections = [[UIImage]]()
+  let _collectionNode: ASCollectionNode!
+  let _layoutInspector = MosaicCollectionViewLayoutInspector()
+  let kNumberOfImages: UInt = 14
+  
+  required init?(coder aDecoder: NSCoder) {
+    let layout = MosaicCollectionViewLayout()
+    layout.numberOfColumns = 3;
+    layout.headerHeight = 44;
+    _collectionNode = ASCollectionNode(frame: CGRect.zero, collectionViewLayout: layout)
+    super.init(coder: aDecoder)
+    layout.delegate = self
+
+    _sections.append([]);
+    var section = 0
+    for idx in 0 ..< kNumberOfImages {
+      let name = String(format: "image_%d.jpg", idx)
+      _sections[section].append(UIImage(named: name)!)
+      if ((idx + 1) % 5 == 0 && idx < kNumberOfImages - 1) {
+        section += 1
+        _sections.append([])
+      }
+    }
+    
+    _collectionNode.dataSource = self;
+    _collectionNode.delegate = self;
+    _collectionNode.view.layoutInspector = _layoutInspector
+    _collectionNode.backgroundColor = UIColor.white
+    _collectionNode.view.isScrollEnabled = true
+    _collectionNode.registerSupplementaryNode(ofKind: UICollectionElementKindSectionHeader)
+  }
+  
+  deinit {
+    _collectionNode.dataSource = nil;
+    _collectionNode.delegate = nil;
+  }
+  
+  override func viewDidLoad() {
+    super.viewDidLoad()
+    self.view.addSubnode(_collectionNode!)
+  }
+  
+  override func viewWillLayoutSubviews() {
+    _collectionNode.frame = self.view.bounds;
+  }
+  
+  func collectionNode(_ collectionNode: ASCollectionNode, nodeForItemAt indexPath: IndexPath) -> ASCellNode {
+    let image = _sections[indexPath.section][indexPath.item]
+    return ImageCellNode(with: image)
+  }
+  
+  
+  func collectionNode(_ collectionNode: ASCollectionNode, nodeForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> ASCellNode {
+    let textAttributes : NSDictionary = [
+      NSFontAttributeName: UIFont.preferredFont(forTextStyle: UIFontTextStyle.headline),
+      NSForegroundColorAttributeName: UIColor.gray
+    ]
+    let textInsets = UIEdgeInsets(top: 11, left: 0, bottom: 11, right: 0)
+    let textCellNode = ASTextCellNode(attributes: textAttributes as! [AnyHashable : Any], insets: textInsets)
+    textCellNode.text = String(format: "Section %zd", indexPath.section + 1)
+    return textCellNode;
+  }
+  
+
+  func numberOfSections(in collectionNode: ASCollectionNode) -> Int {
+    return _sections.count
+  }
+
+  func collectionNode(_ collectionNode: ASCollectionNode, numberOfItemsInSection section: Int) -> Int {
+    return _sections[section].count
+  }
+
+  internal func collectionView(_ collectionView: UICollectionView, layout: MosaicCollectionViewLayout, originalItemSizeAtIndexPath: IndexPath) -> CGSize {
+    return _sections[originalItemSizeAtIndexPath.section][originalItemSizeAtIndexPath.item].size
+  }
+}
+