Give YogaKitSample some love, Convert it to a Swift Project

Summary:
To date, our sample project was lacking. There is still a lot of work that can be done to improve, but, this is a step in the right direction.

Here are the changes in this commit:
1. The project is written in Swift.
2. Created new CollectionView (via [IGListKit](https://github.com/instagram/iglistkit)), making it very easy to add new examples.
3. New examples for basic layouts, and including/excluding layouts on the fly.

Here's a video!

![](https://media.giphy.com/media/l0ExcvTLa0ADdawRa/giphy.gif)
Closes https://github.com/facebook/yoga/pull/392

Reviewed By: emilsjolander

Differential Revision: D4550379

Pulled By: dshahidehpour

fbshipit-source-id: 64a07acf96c1887f1d2ad0c54971fcedb64334a0

YogaKit/YogaKitSample/YogaKitSample/SwiftViewController.swift

@@ -7,35 +7,60 @@
  */
 
 import UIKit
+import IGListKit
 import YogaKit
 
-class SwiftViewController: UIViewController {
-  override func viewDidLoad() {
-    let root = self.view!
-    root.backgroundColor = .red
-    root.yoga.isEnabled = true
-    root.yoga.width = self.view.bounds.size.width
-    root.yoga.height = self.view.bounds.size.height
-    root.yoga.alignItems = .center
-    root.yoga.justifyContent = .center
-
-    let child1 = UIView()
-    child1.backgroundColor = .blue
-    child1.yoga.isEnabled = true
-    child1.yoga.width = 100
-    child1.yoga.height = 10
-
-    let child2 = UIView()
-    child2.backgroundColor = .green
-    child2.frame = CGRect(x: 0, y: 0, width: 200, height: 100)
-
-    let child3 = UIView()
-    child3.backgroundColor = .yellow
-    child3.frame = CGRect(x: 0, y: 0, width: 100, height: 100)
-
-    child2.addSubview(child3)
-    root.addSubview(child1)
-    root.addSubview(child2)
-    root.yoga.applyLayout(preservingOrigin: false)
-  }
+struct DemoItem {
+    let name: String
+}
+
+final class SwiftViewController: UIViewController, IGListAdapterDataSource {
+
+    lazy var adapter: IGListAdapter = {
+        return IGListAdapter(updater: IGListAdapterUpdater(), viewController: self, workingRangeSize: 0)
+    }()
+    let collectionView = IGListCollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
+
+    //MARK: UIViewController
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        title = "YogaKit Examples"
+        view.addSubview(collectionView)
+        adapter.collectionView = collectionView
+        adapter.dataSource = self
+    }
+
+    override func viewDidLayoutSubviews() {
+        super.viewDidLayoutSubviews()
+        collectionView.frame = view.bounds
+    }
+
+
+    //MARK: IGListAdapterDataSource
+
+    func objects(for listAdapter: IGListAdapter) -> [IGListDiffable] {
+        return ["Dustin" as IGListDiffable, "Ryan" as IGListDiffable]
+    }
+
+    func listAdapter(_ listAdapter: IGListAdapter, sectionControllerFor object: Any) -> IGListSectionController {
+        let sizeBlock: IGListSingleSectionCellSizeBlock = { (model, context) in
+            return CGSize(width: (context?.containerSize.width)!, height: 100.0)
+        }
+        let configureBlock: IGListSingleSectionCellConfigureBlock = { (model, cell) in
+            guard let m = model as? String else {
+                return
+            }
+
+            cell.backgroundColor = (m == "Dustin") ? .blue : .red
+        }
+
+        return IGListSingleSectionController(cellClass: UICollectionViewCell.self,
+                                             configureBlock: configureBlock,
+                                             sizeBlock: sizeBlock)
+    }
+
+    func emptyView(for listAdapter: IGListAdapter) -> UIView? {
+        return nil
+    }
 }