Range handlers use recursive actions

fixes #363

AsyncDisplayKit/ASDisplayNode.h

@@ -331,10 +331,19 @@ typedef CALayer *(^ASDisplayNodeLayerBlock)();
  * This method is used to notify the node that it should purge any content that is both expensive to fetch and to
  * retain in memory.
  *
- * @see fetchRemoteData
+ * @see clearRemoteData and fetchRemoteData
  */
 - (void)recursivelyClearRemoteData;
 
+/**
+ * @abstract Calls -fetchRemoteData on the receiver and its subnode hierarchy.
+ *
+ * @discussion Fetches content from remote sources for the current node and all subnodes.
+ *
+ * @see fetchRemoteData and clearRemoteData
+ */
+- (void)recursivelyFetchRemoteData;
+
 /**
  * @abstract Toggle displaying a placeholder over the node that covers content until the node and all subnodes are
  * displayed.

AsyncDisplayKit/ASDisplayNode.mm

@@ -1348,6 +1348,14 @@ static NSInteger incrementIfFound(NSInteger i) {
   // subclass override
 }
 
+- (void)recursivelyFetchRemoteData
+{
+  for (ASDisplayNode *subnode in self.subnodes) {
+    [subnode recursivelyFetchRemoteData];
+  }
+  [self fetchRemoteData];
+}
+
 - (void)clearRemoteData
 {
   // subclass override

AsyncDisplayKit/Details/ASRangeHandlerPreload.mm

@@ -16,13 +16,13 @@
 - (void)node:(ASDisplayNode *)node enteredRangeOfType:(ASLayoutRangeType)rangeType
 {
   ASDisplayNodeAssert(rangeType == ASLayoutRangeTypePreload, @"Preload delegate should not handle other ranges");
-  [node fetchRemoteData];
+  [node recursivelyFetchRemoteData];
 }
 
 - (void)node:(ASDisplayNode *)node exitedRangeOfType:(ASLayoutRangeType)rangeType
 {
   ASDisplayNodeAssert(rangeType == ASLayoutRangeTypePreload, @"Preload delegate should not handle other ranges");
-  [node clearRemoteData];
+  [node recursivelyClearRemoteData];
 }
 
 @end