Merge pull request #1412 from maicki/LastRangeUpdateBeforeClosing

[ASRangeController] Prevent deallocation of dataSource & delegate in Collection & Table when navigating back, during final range update.

AsyncDisplayKit/ASCollectionView.mm

@@ -1139,7 +1139,14 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   // Updating the visible node index paths only for not range managed nodes. Range managed nodes will get their
   // their update in the layout pass
   if (![node supportsRangeManagedInterfaceState]) {
-    [_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:self.scrollDirection];
+    // Grab a strong reference for data source and delegate to be sure they are not going away while executing
+    // the range update. This can happen in range updates while going back in the view controller hierarchy
+    __block id<ASCollectionDataSource> asyncDataSource = _asyncDataSource;
+    __block id<ASCollectionDelegate> asyncDelegate = _asyncDelegate;
+    [_rangeController scheduleRangeUpdateCompletion:^{
+      asyncDataSource = nil;
+      asyncDelegate = nil;
+    }];
   }
 }
 

AsyncDisplayKit/ASTableView.mm

@@ -1072,7 +1072,14 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
   // Updating the visible node index paths only for not range managed nodes. Range managed nodes will get their
   // their update in the layout pass
   if (![node supportsRangeManagedInterfaceState]) {
-    [_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:self.scrollDirection];
+    // Grab a strong reference for data source and delegate to be sure they are not going away while executing
+    // the range update. This can happen in range updates while going back in the view controller hierarchy
+    __block id<ASTableDataSource> asyncDataSource = _asyncDataSource;
+    __block id<ASTableDelegate> asyncDelegate = _asyncDelegate;
+    [_rangeController scheduleRangeUpdateCompletion:^{
+      asyncDataSource = nil;
+      asyncDelegate = nil;
+    }];
   }
 }
 

AsyncDisplayKit/Details/ASRangeController.mm

@@ -27,6 +27,7 @@
   BOOL _didUpdateCurrentRange;
   BOOL _didRegisterForNotifications;
   CFAbsoluteTime _pendingDisplayNodesTimestamp;
+  NSMutableArray *_scheduledRangeUpdateCompletionBlocks;
 }
 
 @end
@@ -46,6 +47,7 @@ static UIApplicationState __ApplicationState = UIApplicationStateActive;
   _rangeIsValid = YES;
   _currentRangeMode = ASLayoutRangeModeInvalid;
   _didUpdateCurrentRange = NO;
+  _scheduledRangeUpdateCompletionBlocks = [NSMutableArray array];
   
   [[[self class] allRangeControllersWeakSet] addObject:self];
   
@@ -111,6 +113,15 @@ static UIApplicationState __ApplicationState = UIApplicationStateActive;
 
 - (void)scheduleRangeUpdate
 {
+  [self scheduleRangeUpdateCompletion:nil];
+}
+
+- (void)scheduleRangeUpdateCompletion:(void (^)(void))completion
+{
+  if (completion) {
+    [_scheduledRangeUpdateCompletionBlocks addObject:completion];
+  }
+ 
   if (_queuedRangeUpdate) {
     return;
   }
@@ -118,8 +129,13 @@ static UIApplicationState __ApplicationState = UIApplicationStateActive;
   // coalesce these events -- handling them multiple times per runloop is noisy and expensive
   _queuedRangeUpdate = YES;
   
+  __block id<ASRangeControllerDataSource> dataSource = _dataSource;
+  __block id<ASRangeControllerDelegate> delegate = _delegate;
   dispatch_async(dispatch_get_main_queue(), ^{
-    [self performRangeUpdate];
+    [self _updateVisibleNodeIndexPaths];
+    
+    dataSource = nil;
+    delegate = nil;
   });
 }
 
@@ -320,6 +336,11 @@ static UIApplicationState __ApplicationState = UIApplicationStateActive;
   _rangeIsValid = YES;
   _queuedRangeUpdate = NO;
   
+  for (void (^completionBlock)(void) in _scheduledRangeUpdateCompletionBlocks) {
+    completionBlock();
+  }
+  [_scheduledRangeUpdateCompletionBlocks removeAllObjects];
+  
 #if ASRangeControllerLoggingEnabled
 //  NSSet *visibleNodePathsSet = [NSSet setWithArray:visibleNodePaths];
 //  BOOL setsAreEqual = [visibleIndexPaths isEqualToSet:visibleNodePathsSet];

AsyncDisplayKit/Details/ASRangeControllerUpdateRangeProtocol+Beta.h

@@ -49,6 +49,12 @@
  */
 - (void)updateCurrentRangeWithMode:(ASLayoutRangeMode)rangeMode;
 
+/**
+ * Schedule a range update and call the completion block if finished. This drives updating the working
+ * ranges, and triggering their actions.
+ */
+- (void)scheduleRangeUpdateCompletion:(void (^)(void))completion;
+
 @end
 
 
@@ -64,7 +70,10 @@
 
 @interface ASViewController (ASRangeControllerUpdateRangeProtocol)
 
-/// Automatically adjust range mode based on view events if the containing node confirms to the ASRangeControllerUpdateRangeProtocol
+/**
+ * Automatically adjust range mode based on view events if the containing node confirms to the
+ * ASRangeControllerUpdateRangeProtocol
+ */
 @property (nonatomic, assign) BOOL automaticallyAdjustRangeModeBasedOnViewEvents;
 
 @end