Implement ASCollectionView. Horizontal scrolling is not supported yet.

AsyncDisplayKit/ASCollectionView.m

@@ -8,6 +8,327 @@
 
 #import "ASCollectionView.h"
 
-@implementation ASCollectionView
+#import "ASAssert.h"
+#import "ASRangeController.h"
+
+
+#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:) ||
+          
+          // 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:)
+          );
+}
+
+
+/**
+ * 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
+{
+  return (_isInterceptedSelector(aSelector) || [_target respondsToSelector:aSelector]);
+}
+
+- (id)forwardingTargetForSelector:(SEL)aSelector
+{
+  if (_isInterceptedSelector(aSelector)) {
+    return _interceptor;
+  }
+  
+  return [_target respondsToSelector:aSelector] ? _target : nil;
+}
+
+@end
+
+
+#pragma mark -
+#pragma mark ASCollectionView.
+
+@interface ASCollectionView () <ASRangeControllerDelegate> {
+  _ASCollectionViewProxy *_proxyDataSource;
+  _ASCollectionViewProxy *_proxyDelegate;
+  
+  ASRangeController *_rangeController;
+}
+
+@end
+
+@implementation ASCollectionView
+
+#pragma mark -
+#pragma mark Lifecycle.
+
+- (instancetype)initWithFrame:(CGRect)frame collectionViewLayout:(UICollectionViewLayout *)layout
+{
+  if (!(self = [super initWithFrame:frame collectionViewLayout:layout]))
+    return nil;
+  
+  _rangeController = [[ASRangeController alloc] init];
+  _rangeController.delegate = self;
+  
+  [self registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"_ASCollectionViewCell"];
+  
+  return self;
+}
+
+
+#pragma mark -
+#pragma mark Overrides.
+
+- (void)reloadData
+{
+  [_rangeController rebuildData];
+  [super reloadData];
+}
+
+- (void)setDataSource:(id<UICollectionViewDataSource>)dataSource
+{
+  ASDisplayNodeAssert(NO, @"ASCollectionView uses asyncDataSource, not UICollectionView's dataSource property.");
+}
+
+- (void)setDelegate:(id<UICollectionViewDelegate>)delegate
+{
+  // Our UIScrollView superclass sets its delegate to nil on dealloc. Only assert if we get a non-nil value here.
+  ASDisplayNodeAssert(delegate == nil, @"ASCollectionView uses asyncDelegate, not UICollectionView's delegate property.");
+}
+
+- (void)setAsyncDataSource:(id<ASCollectionViewDataSource>)asyncDataSource
+{
+  if (_asyncDataSource == asyncDataSource)
+    return;
+  
+  _asyncDataSource = asyncDataSource;
+  _proxyDataSource = [[_ASCollectionViewProxy alloc] initWithTarget:_asyncDataSource interceptor:self];
+  super.dataSource = (id<UICollectionViewDataSource>)_proxyDataSource;
+}
+
+- (void)setAsyncDelegate:(id<ASCollectionViewDelegate>)asyncDelegate
+{
+  if (_asyncDelegate == asyncDelegate)
+    return;
+  
+  _asyncDelegate = asyncDelegate;
+  _proxyDelegate = [[_ASCollectionViewProxy alloc] initWithTarget:_asyncDelegate interceptor:self];
+  super.delegate = (id<UICollectionViewDelegate>)_proxyDelegate;
+}
+
+- (ASRangeTuningParameters)rangeTuningParameters
+{
+  return _rangeController.tuningParameters;
+}
+
+- (void)setRangeTuningParameters:(ASRangeTuningParameters)tuningParameters
+{
+  _rangeController.tuningParameters = tuningParameters;
+}
+
+- (void)appendNodesWithIndexPaths:(NSArray *)indexPaths
+{
+  [_rangeController appendNodesWithIndexPaths:indexPaths];
+}
+
+#pragma mark Assertions.
+
+- (void)throwUnimplementedException
+{
+  [[NSException exceptionWithName:@"UnimplementedException"
+                           reason:@"ASCollectionView's update/editing support is not yet implemented.  Please see ASCollectionView.h."
+                         userInfo:nil] raise];
+}
+
+- (void)insertSections:(NSIndexSet *)sections
+{
+  [self throwUnimplementedException];
+}
+
+- (void)deleteSections:(NSIndexSet *)sections
+{
+  [self throwUnimplementedException];
+}
+
+- (void)reloadSections:(NSIndexSet *)sections
+{
+  [self throwUnimplementedException];
+}
+
+- (void)moveSection:(NSInteger)section toSection:(NSInteger)newSection
+{
+  [self throwUnimplementedException];
+}
+
+- (void)insertItemsAtIndexPaths:(NSArray *)indexPaths
+{
+  [self throwUnimplementedException];
+}
+
+- (void)deleteItemsAtIndexPaths:(NSArray *)indexPaths
+{
+  [self throwUnimplementedException];
+}
+
+- (void)reloadItemsAtIndexPaths:(NSArray *)indexPaths
+{
+  [self throwUnimplementedException];
+}
+
+- (void)moveItemAtIndexPath:(NSIndexPath *)indexPath toIndexPath:(NSIndexPath *)newIndexPath
+{
+    [self throwUnimplementedException];
+}
+
+
+#pragma mark -
+#pragma mark Intercepted selectors.
+
+- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
+{
+  static NSString *reuseIdentifier = @"_ASCollectionViewCell";
+  
+  UICollectionViewCell *cell = [self dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
+  
+  [_rangeController configureContentView:cell.contentView forIndexPath:indexPath];
+  
+  return cell;
+}
+
+- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
+{
+  return [_rangeController calculatedSizeForNodeAtIndexPath:indexPath];
+}
+
+- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
+{
+  return [_rangeController numberOfSizedSections];
+}
+
+- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
+{
+  return [_rangeController numberOfSizedRowsInSection:section];
+}
+
+- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
+{
+  [_rangeController visibleNodeIndexPathsDidChange];
+  
+  if ([_asyncDelegate respondsToSelector:@selector(collectionView:willDisplayNodeForItemAtIndexPath:)]) {
+    [_asyncDelegate collectionView:self willDisplayNodeForItemAtIndexPath:indexPath];
+  }
+}
+
+- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
+{
+  [_rangeController visibleNodeIndexPathsDidChange];
+  
+  if ([_asyncDelegate respondsToSelector:@selector(collectionView:didEndDisplayingNodeForItemAtIndexPath:)]) {
+    [_asyncDelegate collectionView:self didEndDisplayingNodeForItemAtIndexPath:indexPath];
+  }
+}
+
+
+#pragma mark -
+#pragma mark ASRangeControllerDelegate.
+
+- (NSArray *)rangeControllerVisibleNodeIndexPaths:(ASRangeController *)rangeController
+{
+  ASDisplayNodeAssertMainThread();
+  return [self indexPathsForVisibleItems];
+}
+
+- (CGSize)rangeControllerViewportSize:(ASRangeController *)rangeController
+{
+  ASDisplayNodeAssertMainThread();
+  return self.bounds.size;
+}
+
+- (NSInteger)rangeControllerSections:(ASRangeController *)rangeController
+{
+  ASDisplayNodeAssertMainThread();
+  if ([_asyncDataSource respondsToSelector:@selector(numberOfSectionsInCollectionView:)]) {
+    return [_asyncDataSource numberOfSectionsInCollectionView:self];
+  } else {
+    return 1;
+  }
+}
+
+- (NSInteger)rangeController:(ASRangeController *)rangeController rowsInSection:(NSInteger)section
+{
+  ASDisplayNodeAssertMainThread();
+  return [_asyncDataSource collectionView:self numberOfItemsInSection:section];
+}
+
+- (ASCellNode *)rangeController:(ASRangeController *)rangeController nodeForIndexPath:(NSIndexPath *)indexPath
+{
+  ASDisplayNodeAssertNotMainThread();
+  return [_asyncDataSource collectionView:self nodeForItemAtIndexPath:indexPath];
+}
+
+- (CGSize)rangeController:(ASRangeController *)rangeController constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath
+{
+  ASDisplayNodeAssertNotMainThread();
+  //FIXME: Assuming vertical scroll
+  return CGSizeMake(self.bounds.size.width, FLT_MAX);
+}
+
+- (void)rangeController:(ASRangeController *)rangeController didSizeNodesWithIndexPaths:(NSArray *)indexPaths
+{
+  ASDisplayNodeAssertMainThread();
+  [UIView performWithoutAnimation:^{
+    [self performBatchUpdates:^{
+      // -insertItemsAtIndexPaths: is insufficient; UICollectionView also needs to be notified of section changes
+      NSInteger sectionCount = [super numberOfSections];
+      NSInteger newSectionCount = [_rangeController numberOfSizedSections];
+      if (newSectionCount > sectionCount) {
+        NSRange range = NSMakeRange(sectionCount, newSectionCount - sectionCount);
+        NSIndexSet *sections = [NSIndexSet indexSetWithIndexesInRange:range];
+        [super insertSections:sections];
+      }
+      
+      [super insertItemsAtIndexPaths:indexPaths];
+    } completion:nil];
+  }];
+}
 
 @end

AsyncDisplayKit/AsyncDisplayKit.h

@@ -14,4 +14,5 @@
 #import <AsyncDisplayKit/ASTextNode.h>
 
 #import <AsyncDisplayKit/ASTableView.h>
+#import <AsyncDisplayKit/ASCollectionView.h>
 #import <AsyncDisplayKit/ASCellNode.h>