[ASCollectionView / ASPagerNode] Move constrainedSizeForNodeAtIndexPath from the DataSource to the Delegate (#2065)

* Move constrainedSizeForNodeAtIndexPath from the DataSource to the Delegate in ASCollectionView and ASPagerNode

* Fix ASPagerNode declaration of dataSource and delegate

As ASPagerDataSource does not inherit from ASCollectionDataSource it's not possible to declare it as property.

* Update comment

AsyncDisplayKit/ASCollectionView.h

@@ -400,17 +400,6 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (ASCellNode *)collectionView:(ASCollectionView *)collectionView nodeForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
 
-/**
- * Provides the constrained size range for measuring the node at the index path.
- *
- * @param collectionView The sender.
- *
- * @param indexPath The index path of the node.
- *
- * @returns A constrained size range for layout the node at this index path.
- */
-- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath;
-
 /**
  * Indicator to lock the data source for data fetching in async mode.
  * We should not update the data source until the data source has been unlocked. Otherwise, it will incur data inconsistency or exception
@@ -442,6 +431,17 @@ NS_ASSUME_NONNULL_BEGIN
 
 @optional
 
+/**
+ * Provides the constrained size range for measuring the node at the index path.
+ *
+ * @param collectionView The sender.
+ *
+ * @param indexPath The index path of the node.
+ *
+ * @returns A constrained size range for layout the node at this index path.
+ */
+- (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath;
+
 /**
  * Informs the delegate that the collection view will add the node
  * at the given index path to the view hierarchy.

AsyncDisplayKit/ASCollectionView.mm

@@ -151,11 +151,9 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   } _asyncDelegateFlags;
   
   struct {
-    unsigned int asyncDataSourceConstrainedSizeForNode:1;
     unsigned int asyncDataSourceNodeForItemAtIndexPath:1;
     unsigned int asyncDataSourceNodeBlockForItemAtIndexPath:1;
     unsigned int asyncDataSourceNumberOfSectionsInCollectionView:1;
-    unsigned int asyncDataSourceCollectionViewConstrainedSizeForNodeAtIndexPath:1;
   } _asyncDataSourceFlags;
   
   struct {
@@ -354,11 +352,9 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
     _asyncDataSource = asyncDataSource;
     _proxyDataSource = [[ASCollectionViewProxy alloc] initWithTarget:_asyncDataSource interceptor:self];
     
-    _asyncDataSourceFlags.asyncDataSourceConstrainedSizeForNode = [_asyncDataSource respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)];
     _asyncDataSourceFlags.asyncDataSourceNodeForItemAtIndexPath = [_asyncDataSource respondsToSelector:@selector(collectionView:nodeForItemAtIndexPath:)];
     _asyncDataSourceFlags.asyncDataSourceNodeBlockForItemAtIndexPath = [_asyncDataSource respondsToSelector:@selector(collectionView:nodeBlockForItemAtIndexPath:)];
     _asyncDataSourceFlags.asyncDataSourceNumberOfSectionsInCollectionView = [_asyncDataSource respondsToSelector:@selector(numberOfSectionsInCollectionView:)];
-    _asyncDataSourceFlags.asyncDataSourceCollectionViewConstrainedSizeForNodeAtIndexPath = [_asyncDataSource respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)];
 
     // Data-source must implement collectionView:nodeForItemAtIndexPath: or collectionView:nodeBlockForItemAtIndexPath:
     ASDisplayNodeAssertTrue(_asyncDataSourceFlags.asyncDataSourceNodeBlockForItemAtIndexPath || _asyncDataSourceFlags.asyncDataSourceNodeForItemAtIndexPath);

AsyncDisplayKit/ASPagerNode.h

@@ -16,6 +16,8 @@
 @class ASPagerNode;
 @class ASPagerFlowLayout;
 
+NS_ASSUME_NONNULL_BEGIN
+
 #define ASPagerNodeDataSource ASPagerDataSource
 @protocol ASPagerDataSource <NSObject>
 
@@ -52,6 +54,12 @@
  */
 - (ASCellNodeBlock)pagerNode:(ASPagerNode *)pagerNode nodeBlockAtIndex:(NSInteger)index;
 
+@end
+
+@protocol ASPagerDelegate <ASCollectionDelegate>
+
+@optional
+
 /**
  * Provides the constrained size range for measuring the node at the index path.
  *
@@ -63,10 +71,6 @@
 
 @end
 
-@protocol ASPagerDelegate <ASCollectionDelegate>
-
-@end
-
 @interface ASPagerNode : ASCollectionNode
 
 /**
@@ -82,14 +86,15 @@
 /**
  * Data Source is required, and uses a different protocol from ASCollectionNode.
  */
-- (void)setDataSource:(id <ASPagerDataSource>)dataSource;
-- (id <ASPagerDataSource>)dataSource;
+- (void)setDataSource:(nullable id <ASPagerDataSource>)dataSource;
+- (nullable id <ASPagerDataSource>)dataSource;
 
 /**
- * Delegate is optional, and uses the same protocol as ASCollectionNode.
+ * Delegate is optional.
  * This includes UIScrollViewDelegate as well as most methods from UICollectionViewDelegate, like willDisplay...
  */
-@property (nonatomic, weak) id <ASPagerDelegate> delegate;
+- (void)setDelegate:(nullable id <ASPagerDelegate>)delegate;
+- (nullable id <ASPagerDelegate>)delegate;
 
 /**
  * The underlying ASCollectionView object.
@@ -112,3 +117,5 @@
 - (ASCellNode *)nodeForPageAtIndex:(NSInteger)index;
 
 @end
+
+NS_ASSUME_NONNULL_END

AsyncDisplayKit/ASPagerNode.m

@@ -15,18 +15,23 @@
 #import "ASDisplayNode+Subclasses.h"
 #import "ASPagerFlowLayout.h"
 
-@interface ASPagerNode () <ASCollectionDataSource, ASCollectionViewDelegateFlowLayout, ASDelegateProxyInterceptor>
+@interface ASPagerNode () <ASCollectionDataSource, ASCollectionDelegate, ASCollectionViewDelegateFlowLayout, ASDelegateProxyInterceptor>
 {
   ASPagerFlowLayout *_flowLayout;
-  ASPagerNodeProxy *_proxy;
-  __weak id <ASPagerNodeDataSource> _pagerDataSource;
+
+  __weak id <ASPagerDataSource> _pagerDataSource;
+  ASPagerNodeProxy *_proxyDataSource;
   BOOL _pagerDataSourceImplementsNodeBlockAtIndex;
-  BOOL _pagerDataSourceImplementsConstrainedSizeForNode;
+
+  __weak id <ASPagerDelegate> _pagerDelegate;
+  ASPagerNodeProxy *_proxyDelegate;
+  BOOL _pagerDelegateImplementsConstrainedSizeForNode;
 }
 
 @end
 
 @implementation ASPagerNode
+
 @dynamic view, delegate, dataSource;
 
 #pragma mark - Lifecycle
@@ -58,6 +63,7 @@
   [super didLoad];
   
   ASCollectionView *cv = self.view;
+  cv.asyncDelegate = self;
 #if TARGET_OS_IOS
   cv.pagingEnabled = YES;
   cv.scrollsToTop = NO;
@@ -122,9 +128,10 @@
 
 - (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
 {
-  if (_pagerDataSourceImplementsConstrainedSizeForNode) {
-    return [_pagerDataSource pagerNode:self constrainedSizeForNodeAtIndexPath:indexPath];
+  if (_pagerDelegateImplementsConstrainedSizeForNode) {
+    return [_pagerDelegate pagerNode:self constrainedSizeForNodeAtIndexPath:indexPath];
   }
+
   return ASSizeRangeMake(CGSizeZero, self.view.bounds.size);
 }
 
@@ -135,26 +142,38 @@
   return _pagerDataSource;
 }
 
-- (void)setDataSource:(id <ASPagerDataSource>)pagerDataSource
+- (void)setDataSource:(id <ASPagerDataSource>)dataSource
 {
-  if (pagerDataSource != _pagerDataSource) {
-    _pagerDataSource = pagerDataSource;
+  if (dataSource != _pagerDataSource) {
+    _pagerDataSource = dataSource;
     
     _pagerDataSourceImplementsNodeBlockAtIndex = [_pagerDataSource respondsToSelector:@selector(pagerNode:nodeBlockAtIndex:)];
     // Data source must implement pagerNode:nodeBlockAtIndex: or pagerNode:nodeAtIndex:
     ASDisplayNodeAssertTrue(_pagerDataSourceImplementsNodeBlockAtIndex || [_pagerDataSource respondsToSelector:@selector(pagerNode:nodeAtIndex:)]);
     
-    _pagerDataSourceImplementsConstrainedSizeForNode = [_pagerDataSource respondsToSelector:@selector(pagerNode:constrainedSizeForNodeAtIndexPath:)];
+    _proxyDataSource = dataSource ? [[ASPagerNodeProxy alloc] initWithTarget:dataSource interceptor:self] : nil;
     
-    _proxy = pagerDataSource ? [[ASPagerNodeProxy alloc] initWithTarget:pagerDataSource interceptor:self] : nil;
+    super.dataSource = (id <ASCollectionDataSource>)_proxyDataSource;
+  }
+}
 
-    super.dataSource = (id <ASCollectionDataSource>)_proxy;
+- (void)setDelegate:(id<ASPagerDelegate>)delegate
+{
+  if (delegate != _pagerDelegate) {
+    _pagerDelegate = delegate;
+    
+    _pagerDelegateImplementsConstrainedSizeForNode = [_pagerDelegate respondsToSelector:@selector(pagerNode:constrainedSizeForNodeAtIndexPath:)];
+    
+    _proxyDelegate = delegate ? [[ASPagerNodeProxy alloc] initWithTarget:delegate interceptor:self] : nil;
+    
+    super.delegate = (id <ASCollectionDelegate>)_proxyDelegate;
   }
 }
 
 - (void)proxyTargetHasDeallocated:(ASDelegateProxy *)proxy
 {
   [self setDataSource:nil];
+  [self setDelegate:nil];
 }
 
 @end

AsyncDisplayKit/Details/ASCollectionViewFlowLayoutInspector.h

@@ -22,7 +22,7 @@ NS_ASSUME_NONNULL_BEGIN
 @protocol ASCollectionViewLayoutInspecting <NSObject>
 
 /**
- * Asks the inspector to provide a constarained size range for the given collection view node.
+ * Asks the inspector to provide a constrained size range for the given collection view node.
  */
 - (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath;
 

AsyncDisplayKit/Details/ASCollectionViewFlowLayoutInspector.m

@@ -34,7 +34,7 @@ static inline ASSizeRange NodeConstrainedSizeForScrollDirection(ASCollectionView
 @implementation ASCollectionViewLayoutInspector {
   struct {
     unsigned int implementsConstrainedSizeForNodeAtIndexPath:1;
-  } _dataSourceFlags;
+  } _delegateFlags;
 }
 
 #pragma mark Lifecycle
@@ -43,26 +43,26 @@ static inline ASSizeRange NodeConstrainedSizeForScrollDirection(ASCollectionView
 {
   self = [super init];
   if (self != nil) {
-    [self didChangeCollectionViewDataSource:collectionView.asyncDataSource];
+    [self didChangeCollectionViewDelegate:collectionView.asyncDelegate];
   }
   return self;
 }
 
 #pragma mark ASCollectionViewLayoutInspecting
 
-- (void)didChangeCollectionViewDataSource:(id<ASCollectionDataSource>)dataSource
+- (void)didChangeCollectionViewDelegate:(id<ASCollectionDelegate>)delegate
 {
-  if (dataSource == nil) {
-    memset(&_dataSourceFlags, 0, sizeof(_dataSourceFlags));
+  if (delegate == nil) {
+    memset(&_delegateFlags, 0, sizeof(_delegateFlags));
   } else {
-    _dataSourceFlags.implementsConstrainedSizeForNodeAtIndexPath = [dataSource respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)];
+    _delegateFlags.implementsConstrainedSizeForNodeAtIndexPath = [delegate respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)];
   }
 }
 
 - (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
 {
-  if (_dataSourceFlags.implementsConstrainedSizeForNodeAtIndexPath) {
-    return [collectionView.asyncDataSource collectionView:collectionView constrainedSizeForNodeAtIndexPath:indexPath];
+  if (_delegateFlags.implementsConstrainedSizeForNodeAtIndexPath) {
+    return [collectionView.asyncDelegate collectionView:collectionView constrainedSizeForNodeAtIndexPath:indexPath];
   }
   
   return NodeConstrainedSizeForScrollDirection(collectionView);
@@ -99,10 +99,10 @@ static inline ASSizeRange NodeConstrainedSizeForScrollDirection(ASCollectionView
   struct {
     unsigned int implementsReferenceSizeForHeader:1;
     unsigned int implementsReferenceSizeForFooter:1;
+    unsigned int implementsConstrainedSizeForNodeAtIndexPath:1;
   } _delegateFlags;
   
   struct {
-    unsigned int implementsConstrainedSizeForNodeAtIndexPath:1;
     unsigned int implementsNumberOfSectionsInCollectionView:1;
   } _dataSourceFlags;
 }
@@ -132,6 +132,7 @@ static inline ASSizeRange NodeConstrainedSizeForScrollDirection(ASCollectionView
   } else {
     _delegateFlags.implementsReferenceSizeForHeader = [delegate respondsToSelector:@selector(collectionView:layout:referenceSizeForHeaderInSection:)];
     _delegateFlags.implementsReferenceSizeForFooter = [delegate respondsToSelector:@selector(collectionView:layout:referenceSizeForFooterInSection:)];
+    _delegateFlags.implementsConstrainedSizeForNodeAtIndexPath = [delegate respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)];
   }
 }
 
@@ -140,15 +141,14 @@ static inline ASSizeRange NodeConstrainedSizeForScrollDirection(ASCollectionView
   if (dataSource == nil) {
     memset(&_dataSourceFlags, 0, sizeof(_dataSourceFlags));
   } else {
-    _dataSourceFlags.implementsConstrainedSizeForNodeAtIndexPath = [dataSource respondsToSelector:@selector(collectionView:constrainedSizeForNodeAtIndexPath:)];
     _dataSourceFlags.implementsNumberOfSectionsInCollectionView = [dataSource respondsToSelector:@selector(numberOfSectionsInCollectionView:)];
   }
 }
 
 - (ASSizeRange)collectionView:(ASCollectionView *)collectionView constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
 {
-  if (_dataSourceFlags.implementsConstrainedSizeForNodeAtIndexPath) {
-    return [collectionView.asyncDataSource collectionView:collectionView constrainedSizeForNodeAtIndexPath:indexPath];
+  if (_delegateFlags.implementsConstrainedSizeForNodeAtIndexPath) {
+    return [collectionView.asyncDelegate collectionView:collectionView constrainedSizeForNodeAtIndexPath:indexPath];
   }
   
   CGSize itemSize = _layout.itemSize;

examples/AsyncDisplayKitOverview/Sample/Node Containers/OverviewASPagerNode.m

@@ -47,7 +47,7 @@ static UIColor *OverViewASPagerNodeRandomColor() {
 
 #pragma mark - OverviewASPagerNode
 
-@interface OverviewASPagerNode () <ASPagerNodeDataSource>
+@interface OverviewASPagerNode () <ASPagerDataSource, ASPagerDelegate>
 @property (nonatomic, strong) ASPagerNode *node;
 @property (nonatomic, copy) NSArray *data;
 @end
@@ -61,6 +61,7 @@ static UIColor *OverViewASPagerNodeRandomColor() {
     
     _node = [ASPagerNode new];
     _node.dataSource = self;
+    _node.delegate = self;
     [self addSubnode:_node];
     
     return self;

examples/VerticalWithinHorizontalScrolling/Sample/ViewController.m

@@ -19,7 +19,7 @@
 #import "ViewController.h"
 #import "GradientTableNode.h"
 
-@interface ViewController () <ASPagerNodeDataSource>
+@interface ViewController () <ASPagerDataSource, ASPagerDelegate>
 {
   ASPagerNode *_pagerNode;
 }
@@ -38,6 +38,7 @@
   
   _pagerNode = [[ASPagerNode alloc] init];
   _pagerNode.dataSource = self;
+  _pagerNode.delegate = self;
   [ASRangeController setShouldShowRangeDebugOverlay:YES];
   
   // Could implement ASCollectionDelegate if we wanted extra callbacks, like from UIScrollView.