Add empty ASViewController initializer to facilitate subclassing (#1754)

Source/ASViewController.h

@@ -38,6 +38,15 @@ typedef ASTraitCollection * _Nonnull (^ASDisplayTraitsForTraitWindowSizeBlock)(C
  */
 - (instancetype)initWithNode:(DisplayNodeType)node NS_DESIGNATED_INITIALIZER;
 
+/**
+* ASViewController initializer. Useful for interoperability with normal UIViewControllers.
+*
+* @return An ASViewController instance with a nil node whose root view will be backed by a standard UIView as with a normal UIViewController.
+*
+* @see ASVisibilityDepth
+*/
+- (instancetype)init NS_DESIGNATED_INITIALIZER;
+
 NS_ASSUME_NONNULL_END
 
 /**

Source/ASViewController.mm

@@ -64,6 +64,17 @@
   return self;
 }
 
+- (instancetype)init
+{
+  if (!(self = [super initWithNibName:nil bundle:nil])) {
+    return nil;
+  }
+
+  [self _initializeInstance];
+
+  return self;
+}
+
 - (void)_initializeInstance
 {
   if (_node == nil) {

examples/CustomCollectionView-Swift/Sample/ViewController.swift

@@ -17,7 +17,7 @@ class ViewController: ASViewController<ASCollectionNode>, MosaicCollectionViewLa
   let _layoutInspector = MosaicCollectionViewLayoutInspector()
   let kNumberOfImages: UInt = 14
 
-  init() {
+  override init() {
     let layout = MosaicCollectionViewLayout()
     layout.numberOfColumns = 3;
     layout.headerHeight = 44;

examples/LayoutSpecExamples-Swift/Sample/OverviewViewController.swift

@@ -13,7 +13,7 @@ class OverviewViewController: ASViewController<ASTableNode> {
   let tableNode = ASTableNode()
   let layoutExamples: [LayoutExampleNode.Type]
 
-  init() {
+  override init() {
     layoutExamples = [
       HeaderWithRightAndLeftItems.self,
       PhotoWithInsetTextOverlay.self,

examples/Swift/Sample/ViewController.swift

@@ -29,7 +29,7 @@ final class ViewController: ASViewController<ASDisplayNode>, ASTableDataSource,
 
   fileprivate(set) var state: State = .empty
 
-  init() {
+  override init() {
     super.init(node: ASTableNode())
     tableNode.delegate = self
     tableNode.dataSource = self