From 9be2f1db4e05cfbd058ff441f8adfe4da076b133 Mon Sep 17 00:00:00 2001
From: Michael Schneider <mischneider1@gmail.com>
Date: Wed, 29 Jun 2016 11:20:24 -0700
Subject: [PATCH] Prevent calling endUpdatesAnimated:completion: in an
 unbalanced way

---
 .../Details/ASChangeSetDataController.m        | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/AsyncDisplayKit/Details/ASChangeSetDataController.m b/AsyncDisplayKit/Details/ASChangeSetDataController.m
index f6615d1bdb..3a31b8ce82 100644
--- a/AsyncDisplayKit/Details/ASChangeSetDataController.m
+++ b/AsyncDisplayKit/Details/ASChangeSetDataController.m
@@ -18,22 +18,19 @@
 
 #import "ASDataController+Subclasses.h"
 
-@interface ASChangeSetDataController ()
-
-@property (nonatomic, assign) NSUInteger changeSetBatchUpdateCounter;
-@property (nonatomic, strong) _ASHierarchyChangeSet *changeSet;
-
-@end
-
-@implementation ASChangeSetDataController
+@implementation ASChangeSetDataController {
+  NSInteger _changeSetBatchUpdateCounter;
+  _ASHierarchyChangeSet *_changeSet;
+}
 
 #pragma mark - Batching (External API)
 
 - (void)beginUpdates
 {
   ASDisplayNodeAssertMainThread();
-  if (_changeSetBatchUpdateCounter == 0) {
+  if (_changeSetBatchUpdateCounter <= 0) {
     _changeSet = [_ASHierarchyChangeSet new];
+    _changeSetBatchUpdateCounter = 0;
   }
   _changeSetBatchUpdateCounter++;
 }
@@ -43,6 +40,9 @@
   ASDisplayNodeAssertMainThread();
   _changeSetBatchUpdateCounter--;
   
+  // Prevent calling endUpdatesAnimated:completion: in an unbalanced way
+  NSAssert(_changeSetBatchUpdateCounter >= 0, @"endUpdatesAnimated:completion: called without having a balanced beginUpdates call");
+  
   if (_changeSetBatchUpdateCounter == 0) {
     [_changeSet markCompleted];