Revert "[ASCollectionView] Add a "Null Object" for a layout inspector if custom layout is given but no layout inspector" (#1713)

AsyncDisplayKit/ASCollectionView.mm

@@ -98,7 +98,7 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   ASCollectionDataController *_dataController;
   ASRangeController *_rangeController;
   ASCollectionViewLayoutController *_layoutController;
-  id<ASCollectionViewLayoutInspecting> _defaultLayoutInspector;
+  ASCollectionViewFlowLayoutInspector *_flowLayoutInspector;
   NSMutableSet *_cellsForVisibilityUpdates;
   id<ASCollectionViewLayoutFacilitatorProtocol> _layoutFacilitator;
   
@@ -246,19 +246,11 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   // and should not trigger a relayout.
   _ignoreMaxSizeChange = CGSizeEqualToSize(_maxSizeForNodesConstrainedSize, CGSizeZero);
   
+  // Register the default layout inspector delegate for flow layouts only, custom layouts
+  // will need to roll their own ASCollectionViewLayoutInspecting implementation and set a layout delegate
   if ([layout asdk_isFlowLayout]) {
-    // Register the default layout inspector delegate for flow layouts only
-    UICollectionViewFlowLayout *layout = (UICollectionViewFlowLayout *)self.collectionViewLayout;
-    ASDisplayNodeAssertNotNil(layout, @"Collection view layout must be a flow layout to use the built-in inspector");
-    _defaultLayoutInspector = [[ASCollectionViewFlowLayoutInspector alloc] initWithCollectionView:self flowLayout:layout];
-  } else {
-    // Custom layouts will need to roll their own ASCollectionViewLayoutInspecting implementation and set a layout
-    // delegate. In the meantime ASDK provides a custom layout inspector that does not provide any implementation
-    // and asserts for methods that should be implemented in the <ASCollectionViewLayoutInspecting>
-    _defaultLayoutInspector = [[ASCollectionViewCustomLayoutInspector alloc] init];
+    _layoutInspector = [self flowLayoutInspector];
   }
-  _layoutInspector = _defaultLayoutInspector;
-  
   _layoutFacilitator = layoutFacilitator;
   
   _proxyDelegate = [[ASCollectionViewProxy alloc] initWithTarget:nil interceptor:self];
@@ -285,6 +277,19 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   [self setAsyncDataSource:nil];
 }
 
+/**
+ * A layout inspector implementation specific for the sizing behavior of UICollectionViewFlowLayouts
+ */
+- (ASCollectionViewFlowLayoutInspector *)flowLayoutInspector
+{
+  if (_flowLayoutInspector == nil) {
+    UICollectionViewFlowLayout *layout = (UICollectionViewFlowLayout *)self.collectionViewLayout;
+    ASDisplayNodeAssertNotNil(layout, @"Collection view layout must be a flow layout to use the built-in inspector");
+    _flowLayoutInspector = [[ASCollectionViewFlowLayoutInspector alloc] initWithCollectionView:self flowLayout:layout];
+  }
+  return _flowLayoutInspector;
+}
+
 #pragma mark -
 #pragma mark Overrides.
 
@@ -404,10 +409,8 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
 
   super.delegate = (id<UICollectionViewDelegate>)_proxyDelegate;
   
-  if ([_layoutInspector respondsToSelector:@selector(didChangeCollectionViewDelegate:)]) {
   [_layoutInspector didChangeCollectionViewDelegate:asyncDelegate];
 }
-}
 
 - (void)setTuningParameters:(ASRangeTuningParameters)tuningParameters forRangeType:(ASLayoutRangeType)rangeType
 {
@@ -888,21 +891,28 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
 
 - (ASSizeRange)dataController:(ASDataController *)dataController constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
 {
-  ASSizeRange constrainedSize = [_layoutInspector collectionView:self constrainedSizeForNodeAtIndexPath:indexPath];
+  ASSizeRange constrainedSize = kInvalidSizeRange;
+  if (_layoutInspector) {
+    constrainedSize = [_layoutInspector collectionView:self constrainedSizeForNodeAtIndexPath:indexPath];
+  }
+  
   if (!ASSizeRangeEqualToSizeRange(constrainedSize, kInvalidSizeRange)) {
     return constrainedSize;
   }
   
-  CGSize maxSize = _maxSizeForNodesConstrainedSize;
-  if (CGSizeEqualToSize(_maxSizeForNodesConstrainedSize, CGSizeZero)) {
-    maxSize = self.bounds.size;
-  }
+  // TODO: Move this logic into the flow layout inspector. Create a simple inspector for non-flow layouts that don't
+  // implement a custom inspector.
+  if (_asyncDataSourceFlags.asyncDataSourceConstrainedSizeForNode) {
+    constrainedSize = [_asyncDataSource collectionView:self constrainedSizeForNodeAtIndexPath:indexPath];
+  } else {
+    CGSize maxSize = CGSizeEqualToSize(_maxSizeForNodesConstrainedSize, CGSizeZero) ? self.bounds.size : _maxSizeForNodesConstrainedSize;
     if (ASScrollDirectionContainsHorizontalDirection([self scrollableDirections])) {
       maxSize.width = FLT_MAX;
     } else {
       maxSize.height = FLT_MAX;
     }
     constrainedSize = ASSizeRangeMake(CGSizeZero, maxSize);
+  }
   
   return constrainedSize;
 }
@@ -964,16 +974,19 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
 
 - (ASSizeRange)dataController:(ASCollectionDataController *)dataController constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
 {
+  ASDisplayNodeAssert(_layoutInspector != nil, @"To support supplementary nodes in ASCollectionView, it must have a layoutDelegate for layout inspection. (See ASCollectionViewFlowLayoutInspector for an example.)");
   return [_layoutInspector collectionView:self constrainedSizeForSupplementaryNodeOfKind:kind atIndexPath:indexPath];
 }
 
 - (NSUInteger)dataController:(ASCollectionDataController *)dataController supplementaryNodesOfKind:(NSString *)kind inSection:(NSUInteger)section
 {
+  ASDisplayNodeAssert(_layoutInspector != nil, @"To support supplementary nodes in ASCollectionView, it must have a layoutDelegate for layout inspection. (See ASCollectionViewFlowLayoutInspector for an example.)");
   return [_layoutInspector collectionView:self supplementaryNodesOfKind:kind inSection:section];
 }
 
 - (NSUInteger)dataController:(ASCollectionDataController *)dataController numberOfSectionsForSupplementaryNodeOfKind:(NSString *)kind;
 {
+  ASDisplayNodeAssert(_layoutInspector != nil, @"To support supplementary nodes in ASCollectionView, it must have a layoutDelegate for layout inspection. (See ASCollectionViewFlowLayoutInspector for an example.)");
   return [_layoutInspector collectionView:self numberOfSectionsForSupplementaryNodeOfKind:kind];
 }
 

AsyncDisplayKit/Details/ASCollectionViewFlowLayoutInspector.h

@@ -47,17 +47,6 @@
 
 @end
 
-/**
- * Simple "Null Object" inspector for non-flow layouts that does not implement a custom inspector, provides a zero
- * constrained size and throws an exception if methods are called from <ASCollectionViewLayoutInspecting>
- */
-@interface ASCollectionViewCustomLayoutInspector : NSObject <ASCollectionViewLayoutInspecting>
-
-@end
-
-/**
- * A layout inspector implementation specific for the sizing behavior of UICollectionViewFlowLayouts
- */
 @interface ASCollectionViewFlowLayoutInspector : NSObject <ASCollectionViewLayoutInspecting>
 
 @property (nonatomic, weak) UICollectionViewFlowLayout *layout;

AsyncDisplayKit/Details/ASCollectionViewFlowLayoutInspector.m

@@ -13,35 +13,6 @@
 #import "ASAssert.h"
 #import "ASEqualityHelpers.h"
 
-
-
-@implementation ASCollectionViewCustomLayoutInspector
-
-- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
-{
-  return ASSizeRangeMake(CGSizeZero, CGSizeZero);
-}
-
-- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
-{
-  ASDisplayNodeAssert(NO, @"To support supplementary nodes in ASCollectionView, it must have a layoutDelegate for layout inspection. (See ASCollectionViewFlowLayoutInspector for an example.)");
-  return ASSizeRangeMake(CGSizeZero, CGSizeZero);
-}
-
-- (NSUInteger)collectionView:(ASCollectionView *)collectionView numberOfSectionsForSupplementaryNodeOfKind:(NSString *)kind
-{
-  ASDisplayNodeAssert(NO, @"To support supplementary nodes in ASCollectionView, it must have a layoutDelegate for layout inspection. (See ASCollectionViewFlowLayoutInspector for an example.)");
-  return 0;
-}
-
-- (NSUInteger)collectionView:(ASCollectionView *)collectionView supplementaryNodesOfKind:(NSString *)kind inSection:(NSUInteger)section
-{
-  ASDisplayNodeAssert(NO, @"To support supplementary nodes in ASCollectionView, it must have a layoutDelegate for layout inspection. (See ASCollectionViewFlowLayoutInspector for an example.)");
-  return 0;
-}
-
-@end
- 
 @implementation ASCollectionViewFlowLayoutInspector {
   BOOL _delegateImplementsReferenceSizeForHeader;
   BOOL _delegateImplementsReferenceSizeForFooter;
@@ -79,11 +50,8 @@
 
 - (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
 {
-  if ([collectionView.asyncDataSource respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)]) {
-    return [collectionView.asyncDataSource collectionView:collectionView constrainedSizeForNodeAtIndexPath:indexPath];
-  } else {
-    return ASSizeRangeMake(_layout.itemSize, _layout.itemSize);
-  }
+  // TODO: Provide constrained size for flow layout item nodes
+  return ASSizeRangeMake(CGSizeZero, CGSizeZero);
 }
 
 - (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForSupplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath

AsyncDisplayKitTests/ASCollectionViewTests.m

@@ -108,10 +108,7 @@
 {
   UICollectionViewLayout *layout = [[UICollectionViewLayout alloc] init];
   ASCollectionView *collectionView = [[ASCollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout];
-  XCTAssert(collectionView.layoutInspector != nil, @"should automatically set a layout delegate for custom layouts");
-  XCTAssert([collectionView.layoutInspector isKindOfClass:[ASCollectionViewCustomLayoutInspector class]], @"should have a internal custom layout inspector by default");
-  XCTAssert(ASSizeRangeEqualToSizeRange([collectionView.layoutInspector collectionView:collectionView constrainedSizeForNodeAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:0]], ASSizeRangeMake(CGSizeZero, CGSizeZero)), @"should return a zero constrainted size range in internal custom layout inspector");
-  XCTAssertThrows([collectionView.layoutInspector collectionView:collectionView supplementaryNodesOfKind:UICollectionElementKindSectionHeader inSection:0], @"should throw an exception for <ASCollectionViewLayoutInspecting> methods");
+  XCTAssert(collectionView.layoutInspector == nil, @"should not set a layout delegate for custom layouts");
 }
 
 - (void)testThatRegisteringASupplementaryNodeStoresItForIntrospection