New ASDelegateProxy class to unify logic for Table & Collection forwarding. Fix dealloc-during-animation crash.

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -461,6 +461,10 @@
 		DE040EF91C2B40AC004692FF /* ASCollectionViewFlowLayoutInspector.h in Headers */ = {isa = PBXBuildFile; fileRef = 251B8EF41BBB3D690087C538 /* ASCollectionViewFlowLayoutInspector.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		DE6EA3221C14000600183B10 /* ASDisplayNode+FrameworkPrivate.h in Headers */ = {isa = PBXBuildFile; fileRef = DE6EA3211C14000600183B10 /* ASDisplayNode+FrameworkPrivate.h */; };
 		DE6EA3231C14000600183B10 /* ASDisplayNode+FrameworkPrivate.h in Headers */ = {isa = PBXBuildFile; fileRef = DE6EA3211C14000600183B10 /* ASDisplayNode+FrameworkPrivate.h */; };
+		DEC447B51C2B9DBC00C8CBD1 /* ASDelegateProxy.h in Headers */ = {isa = PBXBuildFile; fileRef = DEC447B31C2B9DBC00C8CBD1 /* ASDelegateProxy.h */; };
+		DEC447B61C2B9DBC00C8CBD1 /* ASDelegateProxy.h in Headers */ = {isa = PBXBuildFile; fileRef = DEC447B31C2B9DBC00C8CBD1 /* ASDelegateProxy.h */; };
+		DEC447B71C2B9DBC00C8CBD1 /* ASDelegateProxy.m in Sources */ = {isa = PBXBuildFile; fileRef = DEC447B41C2B9DBC00C8CBD1 /* ASDelegateProxy.m */; };
+		DEC447B81C2B9DBC00C8CBD1 /* ASDelegateProxy.m in Sources */ = {isa = PBXBuildFile; fileRef = DEC447B41C2B9DBC00C8CBD1 /* ASDelegateProxy.m */; };
 		DECBD6E71BE56E1900CF4905 /* ASButtonNode.h in Headers */ = {isa = PBXBuildFile; fileRef = DECBD6E51BE56E1900CF4905 /* ASButtonNode.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		DECBD6E81BE56E1900CF4905 /* ASButtonNode.h in Headers */ = {isa = PBXBuildFile; fileRef = DECBD6E51BE56E1900CF4905 /* ASButtonNode.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		DECBD6E91BE56E1900CF4905 /* ASButtonNode.mm in Sources */ = {isa = PBXBuildFile; fileRef = DECBD6E61BE56E1900CF4905 /* ASButtonNode.mm */; };
@@ -754,6 +758,8 @@
 		D785F6601A74327E00291744 /* ASScrollNode.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASScrollNode.h; sourceTree = "<group>"; };
 		D785F6611A74327E00291744 /* ASScrollNode.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASScrollNode.m; sourceTree = "<group>"; };
 		DE6EA3211C14000600183B10 /* ASDisplayNode+FrameworkPrivate.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "ASDisplayNode+FrameworkPrivate.h"; sourceTree = "<group>"; };
+		DEC447B31C2B9DBC00C8CBD1 /* ASDelegateProxy.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASDelegateProxy.h; sourceTree = "<group>"; };
+		DEC447B41C2B9DBC00C8CBD1 /* ASDelegateProxy.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASDelegateProxy.m; sourceTree = "<group>"; };
 		DECBD6E51BE56E1900CF4905 /* ASButtonNode.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASButtonNode.h; sourceTree = "<group>"; };
 		DECBD6E61BE56E1900CF4905 /* ASButtonNode.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASButtonNode.mm; sourceTree = "<group>"; };
 		EFA731F0396842FF8AB635EE /* libPods-AsyncDisplayKitTests.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = "libPods-AsyncDisplayKitTests.a"; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -1149,6 +1155,8 @@
 		25B171EA1C12242700508A7A /* Data Controller */ = {
 			isa = PBXGroup;
 			children = (
+				DEC447B31C2B9DBC00C8CBD1 /* ASDelegateProxy.h */,
+				DEC447B41C2B9DBC00C8CBD1 /* ASDelegateProxy.m */,
 				251B8EF21BBB3D690087C538 /* ASCollectionDataController.h */,
 				251B8EF31BBB3D690087C538 /* ASCollectionDataController.mm */,
 				464052191A3F83C40061C0BA /* ASDataController.h */,
@@ -1264,6 +1272,7 @@
 				18C2ED7E1B9B7DE800F627B3 /* ASCollectionNode.h in Headers */,
 				257754C01BEE458E00737CA5 /* ASTextNodeWordKerner.h in Headers */,
 				AC3C4A511A1139C100143C57 /* ASCollectionView.h in Headers */,
+				DEC447B51C2B9DBC00C8CBD1 /* ASDelegateProxy.h in Headers */,
 				205F0E1D1B373A2C007741D0 /* ASCollectionViewLayoutController.h in Headers */,
 				AC3C4A541A113EEC00143C57 /* ASCollectionViewProtocols.h in Headers */,
 				058D0A49195D05CB00B7D73C /* ASControlNode+Subclasses.h in Headers */,
@@ -1432,6 +1441,7 @@
 				34EFC7791B701D3600AD841F /* ASLayoutSpecUtilities.h in Headers */,
 				B350625C1B010F070018CF92 /* ASLog.h in Headers */,
 				0442850E1BAA64EC00D16268 /* ASMultidimensionalArrayUtils.h in Headers */,
+				DEC447B61C2B9DBC00C8CBD1 /* ASDelegateProxy.h in Headers */,
 				B35062041B010EFD0018CF92 /* ASMultiplexImageNode.h in Headers */,
 				DECBD6E81BE56E1900CF4905 /* ASButtonNode.h in Headers */,
 				B35062241B010EFD0018CF92 /* ASMutableAttributedStringBuilder.h in Headers */,
@@ -1687,6 +1697,7 @@
 				0549634A1A1EA066000F8E56 /* ASBasicImageDownloader.mm in Sources */,
 				299DA1AA1A828D2900162D41 /* ASBatchContext.mm in Sources */,
 				AC6456091B0A335000CF11B8 /* ASCellNode.m in Sources */,
+				DEC447B71C2B9DBC00C8CBD1 /* ASDelegateProxy.m in Sources */,
 				ACF6ED1D1B17843500DA7C62 /* ASCenterLayoutSpec.mm in Sources */,
 				18C2ED801B9B7DE800F627B3 /* ASCollectionNode.m in Sources */,
 				92DD2FE41BF4B97E0074C9DD /* ASMapNode.mm in Sources */,
@@ -1816,6 +1827,7 @@
 				509E68621B3AEDA5009B9150 /* ASAbstractLayoutController.mm in Sources */,
 				254C6B861BF94F8A003EC431 /* ASTextKitContext.mm in Sources */,
 				34EFC7621B701CA400AD841F /* ASBackgroundLayoutSpec.mm in Sources */,
+				DEC447B81C2B9DBC00C8CBD1 /* ASDelegateProxy.m in Sources */,
 				B35062141B010EFD0018CF92 /* ASBasicImageDownloader.mm in Sources */,
 				B35062161B010EFD0018CF92 /* ASBatchContext.mm in Sources */,
 				AC47D9421B3B891B00AAEE9D /* ASCellNode.m in Sources */,

AsyncDisplayKit.xcworkspace/contents.xcworkspacedata

@@ -1,6 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Workspace
    version = "1.0">
+   <FileRef
+      location = "group:AsyncDisplayKit/Details/ASDelegateProxy.h">
+   </FileRef>
+   <FileRef
+      location = "group:AsyncDisplayKit/Details/ASDelegateProxy.m">
+   </FileRef>
    <FileRef
       location = "group:AsyncDisplayKit.xcodeproj">
    </FileRef>

AsyncDisplayKit/ASCollectionView.mm

@@ -8,6 +8,7 @@
 
 #import "ASAssert.h"
 #import "ASBatchFetching.h"
+#import "ASDelegateProxy.h"
 #import "ASCollectionView.h"
 #import "ASCollectionNode.h"
 #import "ASCollectionDataController.h"
@@ -22,87 +23,6 @@ static const NSUInteger kASCollectionViewAnimationNone = UITableViewRowAnimation
 static const ASSizeRange kInvalidSizeRange = {CGSizeZero, CGSizeZero};
 static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
 
-#pragma mark -
-#pragma mark Proxying.
-
-/**
- * ASCollectionView intercepts and/or overrides a few of UICollectionView's critical data source and delegate methods.
- *
- * Any selector included in this function *MUST* be implemented by ASCollectionView.
- */
-static BOOL _isInterceptedSelector(SEL sel)
-{
-  return (
-          // handled by ASCollectionView node<->cell machinery
-          sel == @selector(collectionView:cellForItemAtIndexPath:) ||
-          sel == @selector(collectionView:layout:sizeForItemAtIndexPath:) ||
-          sel == @selector(collectionView:viewForSupplementaryElementOfKind:atIndexPath:) ||
-          
-          // handled by ASRangeController
-          sel == @selector(numberOfSectionsInCollectionView:) ||
-          sel == @selector(collectionView:numberOfItemsInSection:) ||
-          
-          // used for ASRangeController visibility updates
-          sel == @selector(collectionView:willDisplayCell:forItemAtIndexPath:) ||
-          sel == @selector(collectionView:didEndDisplayingCell:forItemAtIndexPath:) ||
-          
-          // used for batch fetching API
-          sel == @selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)
-          );
-}
-
-
-/**
- * Stand-in for UICollectionViewDataSource and UICollectionViewDelegate.  Any method calls we intercept are routed to ASCollectionView;
- * everything else leaves AsyncDisplayKit safely and arrives at the original intended data source and delegate.
- */
-@interface _ASCollectionViewProxy : NSProxy
-- (instancetype)initWithTarget:(id<NSObject>)target interceptor:(ASCollectionView *)interceptor;
-@end
-
-@implementation _ASCollectionViewProxy {
-  id<NSObject> __weak _target;
-  ASCollectionView * __weak _interceptor;
-}
-
-- (instancetype)initWithTarget:(id<NSObject>)target interceptor:(ASCollectionView *)interceptor
-{
-  // -[NSProxy init] is undefined
-  if (!self) {
-    return nil;
-  }
-  
-  ASDisplayNodeAssert(target, @"target must not be nil");
-  ASDisplayNodeAssert(interceptor, @"interceptor must not be nil");
-  
-  _target = target;
-  _interceptor = interceptor;
-  
-  return self;
-}
-
-- (BOOL)respondsToSelector:(SEL)aSelector
-{
-  ASDisplayNodeAssert(_target, @"target must not be nil"); // catch weak ref's being nilled early
-  ASDisplayNodeAssert(_interceptor, @"interceptor must not be nil");
-  
-  return (_isInterceptedSelector(aSelector) || [_target respondsToSelector:aSelector]);
-}
-
-- (id)forwardingTargetForSelector:(SEL)aSelector
-{
-  ASDisplayNodeAssert(_target, @"target must not be nil"); // catch weak ref's being nilled early
-  ASDisplayNodeAssert(_interceptor, @"interceptor must not be nil");
-  
-  if (_isInterceptedSelector(aSelector)) {
-    return _interceptor;
-  }
-  
-  return [_target respondsToSelector:aSelector] ? _target : nil;
-}
-
-@end
-
 #pragma mark -
 #pragma mark ASCellNode<->UICollectionViewCell bridging.
 
@@ -138,9 +58,9 @@ static BOOL _isInterceptedSelector(SEL sel)
 #pragma mark -
 #pragma mark ASCollectionView.
 
-@interface ASCollectionView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, ASCellNodeLayoutDelegate> {
+@interface ASCollectionView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor> {
-  _ASCollectionViewProxy *_proxyDataSource;
+  ASCollectionViewProxy *_proxyDataSource;
-  _ASCollectionViewProxy *_proxyDelegate;
+  ASCollectionViewProxy *_proxyDelegate;
   
   ASCollectionDataController *_dataController;
   ASRangeController *_rangeController;
@@ -155,6 +75,7 @@ static BOOL _isInterceptedSelector(SEL sel)
   BOOL _collectionViewLayoutImplementsInsetSection;
   BOOL _asyncDataSourceImplementsConstrainedSizeForNode;
   BOOL _queuedNodeSizeUpdate;
+  BOOL _isDeallocating;
   
   ASBatchContext *_batchContext;
   
@@ -244,6 +165,12 @@ static BOOL _isInterceptedSelector(SEL sel)
     _layoutInspector = [self flowLayoutInspector];
   }
   
+  _proxyDelegate = [[ASCollectionViewProxy alloc] initWithTarget:nil interceptor:self];
+  super.delegate = (id<UICollectionViewDelegate>)_proxyDelegate;
+  
+  _proxyDataSource = [[ASCollectionViewProxy alloc] initWithTarget:nil interceptor:self];
+  super.dataSource = (id<UICollectionViewDataSource>)_proxyDataSource;
+  
   _registeredSupplementaryKinds = [NSMutableSet set];
   
   self.backgroundColor = [UIColor whiteColor];
@@ -255,10 +182,10 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 - (void)dealloc
 {
-  // Sometimes the UIKit classes can call back to their delegate even during deallocation.
+  // Sometimes the UIKit classes can call back to their delegate even during deallocation, due to animation completion blocks etc.
-  // This bug might be iOS 7-specific.
+  _isDeallocating = YES;
-  super.delegate  = nil;
+  [self setAsyncDelegate:nil];
-  super.dataSource = nil;
+  [self setAsyncDataSource:nil];
 }
 
 /**
@@ -312,24 +239,35 @@ static BOOL _isInterceptedSelector(SEL sel)
   ASDisplayNodeAssert(delegate == nil, @"ASCollectionView uses asyncDelegate, not UICollectionView's delegate property.");
 }
 
+- (void)proxyTargetHasDeallocated:(ASDelegateProxy *)proxy
+{
+  if (proxy == _proxyDelegate) {
+    [self setAsyncDelegate:nil];
+  } else if (proxy == _proxyDataSource) {
+    [self setAsyncDataSource:nil];
+  }
+}
+
 - (void)setAsyncDataSource:(id<ASCollectionViewDataSource>)asyncDataSource
 {
   // Note: It's common to check if the value hasn't changed and short-circuit but we aren't doing that here to handle
   // the (common) case of nilling the asyncDataSource in the ViewController's dealloc. In this case our _asyncDataSource
   // will return as nil (ARC magic) even though the _proxyDataSource still exists. It's really important to nil out
-  // super.dataSource in this case because calls to _ASTableViewProxy will start failing and cause crashes.
+  // super.dataSource in this case because calls to ASCollectionViewProxy will start failing and cause crashes.
+
+  super.dataSource = nil;
   
   if (asyncDataSource == nil) {
-    super.dataSource = nil;
     _asyncDataSource = nil;
-    _proxyDataSource = nil;
+    _proxyDataSource = _isDeallocating ? nil : [[ASCollectionViewProxy alloc] initWithTarget:nil interceptor:self];
     _asyncDataSourceImplementsConstrainedSizeForNode = NO;
   } else {
     _asyncDataSource = asyncDataSource;
-    _proxyDataSource = [[_ASCollectionViewProxy alloc] initWithTarget:_asyncDataSource interceptor:self];
+    _proxyDataSource = [[ASCollectionViewProxy alloc] initWithTarget:_asyncDataSource interceptor:self];
-    super.dataSource = (id<UICollectionViewDataSource>)_proxyDataSource;
     _asyncDataSourceImplementsConstrainedSizeForNode = ([_asyncDataSource respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)] ? 1 : 0);
   }
+  
+  super.dataSource = (id<UICollectionViewDataSource>)_proxyDataSource;
 }
 
 - (void)setAsyncDelegate:(id<ASCollectionViewDelegate>)asyncDelegate
@@ -337,22 +275,25 @@ static BOOL _isInterceptedSelector(SEL sel)
   // Note: It's common to check if the value hasn't changed and short-circuit but we aren't doing that here to handle
   // the (common) case of nilling the asyncDelegate in the ViewController's dealloc. In this case our _asyncDelegate
   // will return as nil (ARC magic) even though the _proxyDelegate still exists. It's really important to nil out
-  // super.delegate in this case because calls to _ASTableViewProxy will start failing and cause crashes.
+  // super.delegate in this case because calls to ASCollectionViewProxy will start failing and cause crashes.
+  
+  // Order is important here, the asyncDelegate must be callable while nilling super.delegate to avoid random crashes
+  // in UIScrollViewAccessibility.
+
+  super.delegate = nil;
   
   if (asyncDelegate == nil) {
-    // order is important here, the delegate must be callable while nilling super.delegate to avoid random crashes
-    // in UIScrollViewAccessibility.
-    super.delegate = nil;
     _asyncDelegate = nil;
-    _proxyDelegate = nil;
+    _proxyDelegate = _isDeallocating ? nil : [[ASCollectionViewProxy alloc] initWithTarget:nil interceptor:self];
     _asyncDelegateImplementsInsetSection = NO;
   } else {
     _asyncDelegate = asyncDelegate;
-    _proxyDelegate = [[_ASCollectionViewProxy alloc] initWithTarget:_asyncDelegate interceptor:self];
+    _proxyDelegate = [[ASCollectionViewProxy alloc] initWithTarget:_asyncDelegate interceptor:self];
-    super.delegate = (id<UICollectionViewDelegate>)_proxyDelegate;
     _asyncDelegateImplementsInsetSection = ([_asyncDelegate respondsToSelector:@selector(collectionView:layout:insetForSectionAtIndex:)] ? 1 : 0);
   }
   
+  super.delegate = (id<UICollectionViewDelegate>)_proxyDelegate;
+  
   [_layoutInspector didChangeCollectionViewDelegate:asyncDelegate];
 }
 

AsyncDisplayKit/ASTableView.mm

@@ -13,6 +13,7 @@
 #import "ASBatchFetching.h"
 #import "ASChangeSetDataController.h"
 #import "ASCollectionViewLayoutController.h"
+#import "ASDelegateProxy.h"
 #import "ASDisplayNode+FrameworkPrivate.h"
 #import "ASInternalHelpers.h"
 #import "ASLayout.h"
@@ -24,87 +25,6 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
 //#define LOG(...) NSLog(__VA_ARGS__)
 #define LOG(...)
 
-#pragma mark -
-#pragma mark Proxying.
-
-/**
- * ASTableView intercepts and/or overrides a few of UITableView's critical data source and delegate methods.
- *
- * Any selector included in this function *MUST* be implemented by ASTableView.
- */
-static BOOL _isInterceptedSelector(SEL sel)
-{
-  return (
-          // handled by ASTableView node<->cell machinery
-          sel == @selector(tableView:cellForRowAtIndexPath:) ||
-          sel == @selector(tableView:heightForRowAtIndexPath:) ||
-
-          // handled by ASRangeController
-          sel == @selector(numberOfSectionsInTableView:) ||
-          sel == @selector(tableView:numberOfRowsInSection:) ||
-
-          // used for ASRangeController visibility updates
-          sel == @selector(tableView:willDisplayCell:forRowAtIndexPath:) ||
-          sel == @selector(tableView:didEndDisplayingCell:forRowAtIndexPath:) ||
-
-          // used for batch fetching API
-          sel == @selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)
-          );
-}
-
-
-/**
- * Stand-in for UITableViewDataSource and UITableViewDelegate.  Any method calls we intercept are routed to ASTableView;
- * everything else leaves AsyncDisplayKit safely and arrives at the original intended data source and delegate.
- */
-@interface _ASTableViewProxy : NSProxy
-- (instancetype)initWithTarget:(id<NSObject>)target interceptor:(ASTableView *)interceptor;
-@end
-
-@implementation _ASTableViewProxy {
-  id<NSObject> __weak _target;
-  ASTableView * __weak _interceptor;
-}
-
-- (instancetype)initWithTarget:(id<NSObject>)target interceptor:(ASTableView *)interceptor
-{
-  // -[NSProxy init] is undefined
-  if (!self) {
-    return nil;
-  }
-
-  ASDisplayNodeAssert(target, @"target must not be nil");
-  ASDisplayNodeAssert(interceptor, @"interceptor must not be nil");
-
-  _target = target;
-  _interceptor = interceptor;
-
-  return self;
-}
-
-- (BOOL)respondsToSelector:(SEL)aSelector
-{
-  ASDisplayNodeAssert(_target, @"target must not be nil"); // catch weak ref's being nilled early
-  ASDisplayNodeAssert(_interceptor, @"interceptor must not be nil");
-
-  return (_isInterceptedSelector(aSelector) || [_target respondsToSelector:aSelector]);
-}
-
-- (id)forwardingTargetForSelector:(SEL)aSelector
-{
-  ASDisplayNodeAssert(_target, @"target must not be nil"); // catch weak ref's being nilled early
-  ASDisplayNodeAssert(_interceptor, @"interceptor must not be nil");
-
-  if (_isInterceptedSelector(aSelector)) {
-    return _interceptor;
-  }
-
-  return [_target respondsToSelector:aSelector] ? _target : nil;
-}
-
-@end
-
-
 #pragma mark -
 #pragma mark ASCellNode<->UITableViewCell bridging.
 
@@ -156,13 +76,12 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 @end
 
-
 #pragma mark -
 #pragma mark ASTableView
 
-@interface ASTableView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, _ASTableViewCellDelegate, ASCellNodeLayoutDelegate> {
+@interface ASTableView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, _ASTableViewCellDelegate, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor> {
-  _ASTableViewProxy *_proxyDataSource;
+  ASTableViewProxy *_proxyDataSource;
-  _ASTableViewProxy *_proxyDelegate;
+  ASTableViewProxy *_proxyDelegate;
 
   ASFlowLayoutController *_layoutController;
 
@@ -180,6 +99,7 @@ static BOOL _isInterceptedSelector(SEL sel)
   CGFloat _nodesConstrainedWidth;
   BOOL _ignoreNodesConstrainedWidthChange;
   BOOL _queuedNodeHeightUpdate;
+  BOOL _isDeallocating;
 }
 
 @property (atomic, assign) BOOL asyncDataSourceLocked;
@@ -224,6 +144,12 @@ static BOOL _isInterceptedSelector(SEL sel)
   // If the initial size is 0, expect a size change very soon which is part of the initial configuration
   // and should not trigger a relayout.
   _ignoreNodesConstrainedWidthChange = (_nodesConstrainedWidth == 0);
+  
+  _proxyDelegate = [[ASTableViewProxy alloc] initWithTarget:nil interceptor:self];
+  super.delegate = (id<UITableViewDelegate>)_proxyDelegate;
+  
+  _proxyDataSource = [[ASTableViewProxy alloc] initWithTarget:nil interceptor:self];
+  super.dataSource = (id<UITableViewDataSource>)_proxyDataSource;
 
   [self registerClass:_ASTableViewCell.class forCellReuseIdentifier:kCellReuseIdentifier];
 }
@@ -265,9 +191,9 @@ static BOOL _isInterceptedSelector(SEL sel)
 - (void)dealloc
 {
   // Sometimes the UIKit classes can call back to their delegate even during deallocation.
-  // This bug might be iOS 7-specific.
+  _isDeallocating = YES;
-  super.delegate  = nil;
+  [self setAsyncDelegate:nil];
-  super.dataSource = nil;
+  [self setAsyncDataSource:nil];
 }
 
 #pragma mark -
@@ -290,17 +216,19 @@ static BOOL _isInterceptedSelector(SEL sel)
   // Note: It's common to check if the value hasn't changed and short-circuit but we aren't doing that here to handle
   // the (common) case of nilling the asyncDataSource in the ViewController's dealloc. In this case our _asyncDataSource
   // will return as nil (ARC magic) even though the _proxyDataSource still exists. It's really important to nil out
-  // super.dataSource in this case because calls to _ASTableViewProxy will start failing and cause crashes.
+  // super.dataSource in this case because calls to ASTableViewProxy will start failing and cause crashes.
-
+  
+  super.dataSource = nil;
+  
   if (asyncDataSource == nil) {
-    super.dataSource = nil;
     _asyncDataSource = nil;
-    _proxyDataSource = nil;
+    _proxyDataSource = _isDeallocating ? nil : [[ASTableViewProxy alloc] initWithTarget:nil interceptor:self];
   } else {
     _asyncDataSource = asyncDataSource;
-    _proxyDataSource = [[_ASTableViewProxy alloc] initWithTarget:_asyncDataSource interceptor:self];
+    _proxyDataSource = [[ASTableViewProxy alloc] initWithTarget:_asyncDataSource interceptor:self];
-    super.dataSource = (id<UITableViewDataSource>)_proxyDataSource;
   }
+  
+  super.dataSource = (id<UITableViewDataSource>)_proxyDataSource;
 }
 
 - (void)setAsyncDelegate:(id<ASTableViewDelegate>)asyncDelegate
@@ -308,18 +236,30 @@ static BOOL _isInterceptedSelector(SEL sel)
   // Note: It's common to check if the value hasn't changed and short-circuit but we aren't doing that here to handle
   // the (common) case of nilling the asyncDelegate in the ViewController's dealloc. In this case our _asyncDelegate
   // will return as nil (ARC magic) even though the _proxyDelegate still exists. It's really important to nil out
-  // super.delegate in this case because calls to _ASTableViewProxy will start failing and cause crashes.
+  // super.delegate in this case because calls to ASTableViewProxy will start failing and cause crashes.
+  
+  // Order is important here, the asyncDelegate must be callable while nilling super.delegate to avoid random crashes
+  // in UIScrollViewAccessibility.
 
+  super.delegate = nil;
+  
   if (asyncDelegate == nil) {
-    // order is important here, the delegate must be callable while nilling super.delegate to avoid random crashes
-    // in UIScrollViewAccessibility.
-    super.delegate = nil;
     _asyncDelegate = nil;
-    _proxyDelegate = nil; 
+    _proxyDelegate = _isDeallocating ? nil : [[ASTableViewProxy alloc] initWithTarget:nil interceptor:self];
   } else {
     _asyncDelegate = asyncDelegate;
-    _proxyDelegate = [[_ASTableViewProxy alloc] initWithTarget:asyncDelegate interceptor:self];
+    _proxyDelegate = [[ASTableViewProxy alloc] initWithTarget:_asyncDelegate interceptor:self];
-    super.delegate = (id<UITableViewDelegate>)_proxyDelegate;
+  }
+  
+  super.delegate = (id<UITableViewDelegate>)_proxyDelegate;
+}
+
+- (void)proxyTargetHasDeallocated:(ASDelegateProxy *)proxy
+{
+  if (proxy == _proxyDelegate) {
+    [self setAsyncDelegate:nil];
+  } else if (proxy == _proxyDataSource) {
+    [self setAsyncDataSource:nil];
   }
 }
 

AsyncDisplayKit/Details/ASDelegateProxy.h

@@ -0,0 +1,51 @@
+/* Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+@class ASDelegateProxy;
+@protocol ASDelegateProxyInterceptor
+@required
+// Called if the target object is discovered to be nil if it had been non-nil at init time.
+// This happens if the object is deallocated, because the proxy must maintain a weak reference to avoid cycles.
+// Though the target object may become nil, the interceptor must not; it is assumed the interceptor owns the proxy.
+- (void)proxyTargetHasDeallocated:(ASDelegateProxy *)proxy;
+@end
+
+/**
+ * Stand-in for delegates like UITableView or UICollectionView's delegate / dataSource.
+ * Any selectors flagged by "interceptsSelector" are routed to the interceptor object and are not delivered to the target.
+ * Everything else leaves AsyncDisplayKit safely and arrives at the original target object.
+ */
+
+@interface ASDelegateProxy : NSProxy
+
+- (instancetype)initWithTarget:(id<NSObject>)target interceptor:(id <ASDelegateProxyInterceptor>)interceptor;
+
+// This method must be overridden by a subclass.
+- (BOOL)interceptsSelector:(SEL)selector;
+
+@end
+
+/**
+ * ASTableView intercepts and/or overrides a few of UITableView's critical data source and delegate methods.
+ *
+ * Any selector included in this function *MUST* be implemented by ASTableView.
+ */
+
+@interface ASTableViewProxy : ASDelegateProxy
+@end
+
+/**
+ * ASCollectionView intercepts and/or overrides a few of UICollectionView's critical data source and delegate methods.
+ *
+ * Any selector included in this function *MUST* be implemented by ASCollectionView.
+ */
+
+@interface ASCollectionViewProxy : ASDelegateProxy
+@end

AsyncDisplayKit/Details/ASDelegateProxy.m

@@ -0,0 +1,117 @@
+/* Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "ASDelegateProxy.h"
+#import "ASTableView.h"
+#import "ASCollectionView.h"
+#import "ASAssert.h"
+
+@implementation ASTableViewProxy
+
+- (BOOL)interceptsSelector:(SEL)selector
+{
+  return (
+          // handled by ASTableView node<->cell machinery
+          selector == @selector(tableView:cellForRowAtIndexPath:) ||
+          selector == @selector(tableView:heightForRowAtIndexPath:) ||
+          
+          // handled by ASRangeController
+          selector == @selector(numberOfSectionsInTableView:) ||
+          selector == @selector(tableView:numberOfRowsInSection:) ||
+          
+          // used for ASRangeController visibility updates
+          selector == @selector(tableView:willDisplayCell:forRowAtIndexPath:) ||
+          selector == @selector(tableView:didEndDisplayingCell:forRowAtIndexPath:) ||
+          
+          // used for batch fetching API
+          selector == @selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)
+          );
+}
+
+@end
+
+@implementation ASCollectionViewProxy
+
+- (BOOL)interceptsSelector:(SEL)selector
+{
+  return (
+          // handled by ASCollectionView node<->cell machinery
+          selector == @selector(collectionView:cellForItemAtIndexPath:) ||
+          selector == @selector(collectionView:layout:sizeForItemAtIndexPath:) ||
+          selector == @selector(collectionView:viewForSupplementaryElementOfKind:atIndexPath:) ||
+          
+          // handled by ASRangeController
+          selector == @selector(numberOfSectionsInCollectionView:) ||
+          selector == @selector(collectionView:numberOfItemsInSection:) ||
+          
+          // used for ASRangeController visibility updates
+          selector == @selector(collectionView:willDisplayCell:forItemAtIndexPath:) ||
+          selector == @selector(collectionView:didEndDisplayingCell:forItemAtIndexPath:) ||
+          
+          // used for batch fetching API
+          selector == @selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)
+          );
+}
+
+@end
+
+@implementation ASDelegateProxy {
+  id <NSObject> __weak _target;
+  id <ASDelegateProxyInterceptor> __weak _interceptor;
+}
+
+- (instancetype)initWithTarget:(id <NSObject>)target interceptor:(id <ASDelegateProxyInterceptor>)interceptor
+{
+  // -[NSProxy init] is undefined
+  if (!self) {
+    return nil;
+  }
+  
+  ASDisplayNodeAssert(interceptor, @"interceptor must not be nil");
+  
+  _target = target ? : [NSNull null];
+  _interceptor = interceptor;
+  
+  return self;
+}
+
+- (BOOL)respondsToSelector:(SEL)aSelector
+{
+  ASDisplayNodeAssert(_interceptor, @"interceptor must not be nil");
+  
+  if ([self interceptsSelector:aSelector]) {
+    return YES;
+  } else {
+    // Also return NO if _target has become nil due to zeroing weak reference (or placeholder initialization).
+    return [_target respondsToSelector:aSelector];
+  }
+}
+
+- (id)forwardingTargetForSelector:(SEL)aSelector
+{
+  ASDisplayNodeAssert(_interceptor, @"interceptor must not be nil");
+  
+  if ([self interceptsSelector:aSelector]) {
+    return _interceptor;
+  } else {
+    if (_target) {
+      return [_target respondsToSelector:aSelector] ? _target : nil;
+    } else {
+      [_interceptor proxyTargetHasDeallocated:self];
+      return nil;
+    }
+  }
+}
+
+- (BOOL)interceptsSelector:(SEL)selector
+{
+  ASDisplayNodeAssert(NO, @"This method must be overridden by subclasses.");
+  return NO;
+}
+
+@end

AsyncDisplayKitTests/ASBasicImageDownloaderTests.m

@@ -11,45 +11,38 @@
 #import <AsyncDisplayKit/ASBasicImageDownloader.h>
 
 // Z in the name to delay running until after the test instance is operating normally.
-@interface ASZBasicImageDownloaderTests : XCTestCase
+@interface ASBasicImageDownloaderTests : XCTestCase
 
 @end
 
-@implementation ASZBasicImageDownloaderTests
+@implementation ASBasicImageDownloaderTests
 
 - (void)testAsynchronouslyDownloadTheSameURLTwice
 {
     ASBasicImageDownloader *downloader = [ASBasicImageDownloader sharedImageDownloader];
     
     NSURL *URL = [NSURL URLWithString:@"http://wrongPath/wrongResource.png"];
-    
+  
-    dispatch_group_t group = dispatch_group_create();
-    
     __block BOOL firstDone = NO;
     
-    dispatch_group_enter(group);
     [downloader downloadImageWithURL:URL
                        callbackQueue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
                downloadProgressBlock:nil
                           completion:^(CGImageRef image, NSError *error) {
                               firstDone = YES;
-                              dispatch_group_leave(group);
                           }];
     
     __block BOOL secondDone = NO;
     
-    dispatch_group_enter(group);
     [downloader downloadImageWithURL:URL
                        callbackQueue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
                downloadProgressBlock:nil
                           completion:^(CGImageRef image, NSError *error) {
                               secondDone = YES;
-                              dispatch_group_leave(group);
                           }];
-    
+  
-    XCTAssert(0 == dispatch_group_wait(group, dispatch_time(0, 10 * 1000000000)), @"URL loading takes too long");
+    sleep(3);
-    
+    XCTAssert(firstDone && secondDone, @"Not all ASBasicImageDownloader completion handlers have been called after 3 seconds");
-    XCTAssert(firstDone && secondDone, @"Not all handlers has been called");
 }
 
 @end

examples/ASCollectionView/Sample.xcodeproj/project.pbxproj

@@ -15,6 +15,7 @@
 		AC3C4A6A1A11F47200143C57 /* ViewController.m in Sources */ = {isa = PBXBuildFile; fileRef = AC3C4A691A11F47200143C57 /* ViewController.m */; };
 		AC3C4A8E1A11F80C00143C57 /* Images.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = AC3C4A8D1A11F80C00143C57 /* Images.xcassets */; };
 		FABD6D156A3EB118497E5CE6 /* libPods.a in Frameworks */ = {isa = PBXBuildFile; fileRef = F02BAF78E68BC56FD8C161B7 /* libPods.a */; };
+		FC3FCA801C2B1564009F6D6D /* PresentingViewController.m in Sources */ = {isa = PBXBuildFile; fileRef = FC3FCA7F1C2B1564009F6D6D /* PresentingViewController.m */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -34,6 +35,8 @@
 		AC3C4A8D1A11F80C00143C57 /* Images.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Images.xcassets; sourceTree = "<group>"; };
 		CD1ABB23007FEDB31D8C1978 /* Pods.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = Pods.release.xcconfig; path = "Pods/Target Support Files/Pods/Pods.release.xcconfig"; sourceTree = "<group>"; };
 		F02BAF78E68BC56FD8C161B7 /* libPods.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libPods.a; sourceTree = BUILT_PRODUCTS_DIR; };
+		FC3FCA7E1C2B1564009F6D6D /* PresentingViewController.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = PresentingViewController.h; sourceTree = "<group>"; };
+		FC3FCA7F1C2B1564009F6D6D /* PresentingViewController.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = PresentingViewController.m; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -82,6 +85,8 @@
 				AC3C4A661A11F47200143C57 /* AppDelegate.m */,
 				AC3C4A681A11F47200143C57 /* ViewController.h */,
 				AC3C4A691A11F47200143C57 /* ViewController.m */,
+				FC3FCA7E1C2B1564009F6D6D /* PresentingViewController.h */,
+				FC3FCA7F1C2B1564009F6D6D /* PresentingViewController.m */,
 				AC3C4A8D1A11F80C00143C57 /* Images.xcassets */,
 				AC3C4A611A11F47200143C57 /* Supporting Files */,
 				9B92C87F1BC17D3000EE46B2 /* SupplementaryNode.h */,
@@ -125,7 +130,6 @@
 				AC3C4A5B1A11F47200143C57 /* Frameworks */,
 				AC3C4A5C1A11F47200143C57 /* Resources */,
 				A6902C454C7661D0D277AC62 /* Copy Pods Resources */,
-				EC37EEC9933F5786936BFE7C /* Embed Pods Frameworks */,
 			);
 			buildRules = (
 			);
@@ -196,21 +200,6 @@
 			shellScript = "\"${SRCROOT}/Pods/Target Support Files/Pods/Pods-resources.sh\"\n";
 			showEnvVarsInLog = 0;
 		};
-		EC37EEC9933F5786936BFE7C /* Embed Pods Frameworks */ = {
-			isa = PBXShellScriptBuildPhase;
-			buildActionMask = 2147483647;
-			files = (
-			);
-			inputPaths = (
-			);
-			name = "Embed Pods Frameworks";
-			outputPaths = (
-			);
-			runOnlyForDeploymentPostprocessing = 0;
-			shellPath = /bin/sh;
-			shellScript = "\"${SRCROOT}/Pods/Target Support Files/Pods/Pods-frameworks.sh\"\n";
-			showEnvVarsInLog = 0;
-		};
 		F868CFBB21824CC9521B6588 /* Check Pods Manifest.lock */ = {
 			isa = PBXShellScriptBuildPhase;
 			buildActionMask = 2147483647;
@@ -236,6 +225,7 @@
 				25FDEC921BF31EE700CEB123 /* ItemNode.m in Sources */,
 				AC3C4A6A1A11F47200143C57 /* ViewController.m in Sources */,
 				9B92C8811BC17D3000EE46B2 /* SupplementaryNode.m in Sources */,
+				FC3FCA801C2B1564009F6D6D /* PresentingViewController.m in Sources */,
 				AC3C4A671A11F47200143C57 /* AppDelegate.m in Sources */,
 				AC3C4A641A11F47200143C57 /* main.m in Sources */,
 			);

examples/ASCollectionView/Sample.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "group:Sample.xcodeproj">
+   </FileRef>
+   <FileRef
+      location = "group:Pods/Pods.xcodeproj">
+   </FileRef>
+</Workspace>

examples/ASCollectionView/Sample/AppDelegate.h

@@ -11,6 +11,8 @@
 
 #import <UIKit/UIKit.h>
 
+#define SIMULATE_WEB_RESPONSE 0
+
 @interface AppDelegate : UIResponder <UIApplicationDelegate>
 
 @property (strong, nonatomic) UIWindow *window;

examples/ASCollectionView/Sample/AppDelegate.m

@@ -11,6 +11,7 @@
 
 #import "AppDelegate.h"
 
+#import "PresentingViewController.h"
 #import "ViewController.h"
 
 @implementation AppDelegate
@@ -31,10 +32,14 @@
 - (void)pushNewViewControllerAnimated:(BOOL)animated
 {
   UINavigationController *navController = (UINavigationController *)self.window.rootViewController;
-  
+
+#if SIMULATE_WEB_RESPONSE
+  UIViewController *viewController = [[PresentingViewController alloc] init];
+#else
   UIViewController *viewController = [[ViewController alloc] init];
   viewController.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Push Another Copy" style:UIBarButtonItemStylePlain target:self action:@selector(pushNewViewController)];
-
+#endif
+  
   [navController pushViewController:viewController animated:animated];
 }
 

examples/ASCollectionView/Sample/PresentingViewController.h

@@ -0,0 +1,13 @@
+//
+//  PresentingViewController.h
+//  Sample
+//
+//  Created by Tom King on 12/23/15.
+//  Copyright © 2015 Facebook. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+
+@interface PresentingViewController : UIViewController
+
+@end

examples/ASCollectionView/Sample/PresentingViewController.m

@@ -0,0 +1,30 @@
+//
+//  PresentingViewController.m
+//  Sample
+//
+//  Created by Tom King on 12/23/15.
+//  Copyright © 2015 Facebook. All rights reserved.
+//
+
+#import "PresentingViewController.h"
+#import "ViewController.h"
+
+@interface PresentingViewController ()
+
+@end
+
+@implementation PresentingViewController
+
+- (void)viewDidLoad
+{
+  [super viewDidLoad];
+  self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Push Details" style:UIBarButtonItemStylePlain target:self action:@selector(pushNewViewController)];
+}
+
+- (void)pushNewViewController
+{
+  ViewController *controller = [[ViewController alloc] init];
+  [self.navigationController pushViewController:controller animated:true];
+}
+
+@end

examples/ASCollectionView/Sample/ViewController.m

@@ -18,6 +18,7 @@
 @interface ViewController () <ASCollectionViewDataSource, ASCollectionViewDelegateFlowLayout>
 {
   ASCollectionView *_collectionView;
+  NSArray *_data;
 }
 
 @end
@@ -37,7 +38,7 @@
   layout.headerReferenceSize = CGSizeMake(50.0, 50.0);
   layout.footerReferenceSize = CGSizeMake(50.0, 50.0);
   
-  _collectionView = [[ASCollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout asyncDataFetching:YES];
+  _collectionView = [[ASCollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout];
   _collectionView.asyncDataSource = self;
   _collectionView.asyncDelegate = self;
   _collectionView.backgroundColor = [UIColor whiteColor];
@@ -45,8 +46,10 @@
   [_collectionView registerSupplementaryNodeOfKind:UICollectionElementKindSectionHeader];
   [_collectionView registerSupplementaryNodeOfKind:UICollectionElementKindSectionFooter];
   
+#if !SIMULATE_WEB_RESPONSE
   self.navigationItem.leftItemsSupplementBackButton = YES;
   self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:@selector(reloadTapped)];
+#endif
   
   return self;
 }
@@ -56,6 +59,31 @@
   [super viewDidLoad];
   
   [self.view addSubview:_collectionView];
+
+#if SIMULATE_WEB_RESPONSE
+  __weak typeof(self) weakSelf = self;
+  void(^mockWebService)() = ^{
+    NSLog(@"ViewController \"got data from a web service\"");
+    ViewController *strongSelf = weakSelf;
+    if (strongSelf != nil)
+    {
+      NSLog(@"ViewController is not nil");
+      strongSelf->_data = [[NSArray alloc] init];
+      [strongSelf->_collectionView performBatchUpdates:^{
+        [strongSelf->_collectionView insertSections:[[NSIndexSet alloc] initWithIndexesInRange:NSMakeRange(0, 100)]];
+      } completion:nil];
+      NSLog(@"ViewController finished updating collectionView");
+    }
+    else {
+      NSLog(@"ViewController is nil - won't update collectionView");
+    }
+  };
+  
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), mockWebService);
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
+    [self.navigationController popViewControllerAnimated:YES];
+  });
+#endif
 }
 
 - (void)viewWillLayoutSubviews
@@ -101,7 +129,11 @@
 
 - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
 {
+#if SIMULATE_WEB_RESPONSE
+  return _data == nil ? 0 : 100;
+#else
   return 100;
+#endif
 }
 
 - (void)collectionViewLockDataSource:(ASCollectionView *)collectionView
@@ -125,4 +157,11 @@
   return UIEdgeInsetsMake(20.0, 20.0, 20.0, 20.0);
 }
 
+#if SIMULATE_WEB_RESPONSE
+-(void)dealloc
+{
+  NSLog(@"ViewController is deallocing");
+}
+#endif
+
 @end