Merge pull request #1791 from colinmcardell/ASCollectionDataController_supplementaryNodeOfKind-fix

[ASCollectionDataController] Exposing -supplementaryNodeOfKind

AsyncDisplayKit/ASCollectionView.h

@@ -278,9 +278,20 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @param indexPath The index path of the requested node.
  *
- * @returns a node for display at this indexpath.
+ * @returns a node for display at this indexpath or nil
  */
-- (ASCellNode *)nodeForItemAtIndexPath:(NSIndexPath *)indexPath;
+- (nullable ASCellNode *)nodeForItemAtIndexPath:(NSIndexPath *)indexPath;
+
+
+/**
+ * Similar to -supplementaryViewForElementKind:atIndexPath:
+ *
+ * @param elementKind The kind of supplementary node to locate.
+ * @param indexPath The index path of the requested supplementary node.
+ *
+ * @returns The specified supplementary node or nil
+ */
+- (nullable ASCellNode *)supplementaryNodeForElementKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath;
 
 /**
  * Similar to -indexPathForCell:.

AsyncDisplayKit/ASCollectionView.mm

@@ -440,6 +440,11 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   return [_dataController nodeAtIndexPath:indexPath];
 }
 
+- (ASCellNode *)supplementaryNodeForElementKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath
+{
+  return [_dataController supplementaryNodeOfKind:elementKind atIndexPath:indexPath];
+}
+
 - (NSIndexPath *)indexPathForNode:(ASCellNode *)cellNode
 {
   return [_dataController indexPathForNode:cellNode];
@@ -592,6 +597,7 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   NSString *identifier = [self __reuseIdentifierForKind:kind];
   UICollectionReusableView *view = [self dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:identifier forIndexPath:indexPath];
   ASCellNode *node = [_dataController supplementaryNodeOfKind:kind atIndexPath:indexPath];
+  ASDisplayNodeAssert(node != nil, @"Supplementary node should exist.  Kind = %@, indexPath = %@, collectionDataSource = %@", kind, indexPath, self);
   [_rangeController configureContentView:view forCellNode:node];
   return view;
 }

AsyncDisplayKit/Details/ASCollectionDataController.mm

@@ -257,8 +257,7 @@
       return nodesOfKindInSection[itemIndex];
     }
   }
-  ASDisplayNodeAssert(NO, @"Supplementary node should exist.  Kind = %@, indexPath = %@, collectionDataSource = %@", kind, indexPath, self.collectionDataSource);
+  return nil;
-  return [[ASCellNode alloc] init];
 }
 
 #pragma mark - Private Helpers