From 15aa784fe829666f0b31e29a9439c0eceb620093 Mon Sep 17 00:00:00 2001
From: Hannah Troisi <htroisi@pinterest.com>
Date: Fri, 21 Oct 2016 10:19:27 -0700
Subject: [PATCH] [ASCollectionNode] add -indexPathsForVisibleNodes (#2451)

---
 AsyncDisplayKit/ASCollectionNode.h  |  6 ++++++
 AsyncDisplayKit/ASCollectionNode.mm | 13 +++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/AsyncDisplayKit/ASCollectionNode.h b/AsyncDisplayKit/ASCollectionNode.h
index ab4c06ce03..b36d94ee88 100644
--- a/AsyncDisplayKit/ASCollectionNode.h
+++ b/AsyncDisplayKit/ASCollectionNode.h
@@ -313,6 +313,12 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (nullable NSIndexPath *)indexPathForNode:(ASCellNode *)cellNode AS_WARN_UNUSED_RESULT;
 
+/**
+ * Retrieve the index paths of all visible items.
+ *
+ * @return an array containing the index paths of all visible items. This must be called on the main thread.
+ */
+- (NSArray<__kindof NSIndexPath *> *)indexPathsForVisibleItems AS_WARN_UNUSED_RESULT;
 
 /**
  * Retrieves the context object for the given section, as provided by the data source in
diff --git a/AsyncDisplayKit/ASCollectionNode.mm b/AsyncDisplayKit/ASCollectionNode.mm
index 07d2c8c5a4..ab6123be31 100644
--- a/AsyncDisplayKit/ASCollectionNode.mm
+++ b/AsyncDisplayKit/ASCollectionNode.mm
@@ -295,6 +295,19 @@
   return [self.dataController indexPathForNode:cellNode];
 }
 
+- (NSArray<__kindof NSIndexPath *> *)indexPathsForVisibleItems
+{
+  NSMutableArray *indexPathsArray = [NSMutableArray new];
+  for (ASCellNode *cell in [self visibleNodes]) {
+    NSIndexPath *indexPath = [self indexPathForNode:cell];
+    if (indexPath) {
+      [indexPathsArray addObject:indexPath];
+    }
+  }
+  return indexPathsArray;
+}
+
+
 - (ASCellNode *)nodeForItemAtIndexPath:(NSIndexPath *)indexPath
 {
   return [self.dataController nodeAtIndexPath:indexPath];