ASCollectionView batch API

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -138,7 +138,6 @@
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-<<<<<<< HEAD
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@@ -146,6 +145,7 @@
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 		299DA1A91A828D2900162D41 /* ASBatchContext.h in Headers */ = {isa = PBXBuildFile; fileRef = 299DA1A71A828D2900162D41 /* ASBatchContext.h */; };
+		299DA1A91A828D2900162D41 /* ASBatchContext.h in Headers */ = {isa = PBXBuildFile; fileRef = 299DA1A71A828D2900162D41 /* ASBatchContext.h */; settings = {ATTRIBUTES = (Public, ); }; };
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@@ -293,7 +293,6 @@
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-<<<<<<< HEAD
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AsyncDisplayKit/ASCollectionView.h

@@ -11,6 +11,7 @@
 #import <AsyncDisplayKit/ASRangeController.h>
 #import <AsyncDisplayKit/ASCollectionViewProtocols.h>
 #import <AsyncDisplayKit/ASBaseDefines.h>
+#import <AsyncDisplayKit/ASBatchContext.h>
 
 
 @class ASCellNode;
@@ -62,6 +63,13 @@
  */
 - (instancetype)initWithFrame:(CGRect)frame collectionViewLayout:(UICollectionViewLayout *)layout asyncDataFetching:(BOOL)asyncDataFetchingEnabled;
 
+/**
+ * The number of screens left to scroll before the delegate -collectionView:beginBatchFetchingWithContext: is called.
+ *
+ * Defaults to one screenful.
+ */
+@property (nonatomic, assign) CGFloat leadingScreensForBatching;
+
 /**
  * Reload everything from scratch, destroying the working range and all cached nodes.
  *
@@ -166,6 +174,34 @@
 - (void)collectionView:(ASCollectionView *)collectionView willDisplayNodeForItemAtIndexPath:(NSIndexPath *)indexPath;
 - (void)collectionView:(ASCollectionView *)collectionView didEndDisplayingNodeForItemAtIndexPath:(NSIndexPath*)indexPath;
 
+/**
+ * Tell the collectionView if batch fetching should begin.
+ *
+ * @param collectionView The sender.
+ *
+ * @discussion Use this method to conditionally fetch batches. Example use cases are: limiting the total number of
+ * objects that can be fetched or no network connection.
+ *
+ * If not implemented, the collectionView assumes that it should notify its asyncDelegate when batch fetching
+ * should occur.
+ */
+- (BOOL)shouldBatchFetchForCollectionView:(UICollectionView *)collectionView;
+
+/**
+ * Receive a message that the collectionView is near the end of its data set and more data should be fetched if 
+ * necessary.
+ *
+ * @param tableView The sender.
+ * @param context A context object that must be notified when the batch fetch is completed.
+ *
+ * @discussion You must eventually call -completeBatchFetching: with an argument of YES in order to receive future
+ * notifications to do batch fetches.
+ *
+ * UICollectionView currently only supports batch events for tail loads. If you require a head load, consider
+ * implementing a UIRefreshControl.
+ */
+- (void)collectionView:(UICollectionView *)collectionView beginBatchFetchingWithContext:(ASBatchContext *)context;
+
 @end
 
 @interface ASCollectionView (Deprecated)

AsyncDisplayKit/ASCollectionView.mm

@@ -38,7 +38,10 @@ static BOOL _isInterceptedSelector(SEL sel)
           
           // used for ASRangeController visibility updates
           sel == @selector(collectionView:willDisplayCell:forItemAtIndexPath:) ||
-          sel == @selector(collectionView:didEndDisplayingCell:forItemAtIndexPath:)
+          sel == @selector(collectionView:didEndDisplayingCell:forItemAtIndexPath:) ||
+
+          // used for batch fetching API
+          sel == @selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)
           );
 }
 
@@ -103,6 +106,8 @@ static BOOL _isInterceptedSelector(SEL sel)
   NSMutableArray *_batchUpdateBlocks;
 
   BOOL _asyncDataFetchingEnabled;
+
+  ASBatchContext *_batchContext;
 }
 
 @property (atomic, assign) BOOL asyncDataSourceLocked;
@@ -137,6 +142,8 @@ static BOOL _isInterceptedSelector(SEL sel)
   _dataController.delegate = _rangeController;
   _dataController.dataSource = self;
 
+  _batchContext = [[ASBatchContext alloc] init];
+
   _proxyDelegate = [[_ASCollectionViewProxy alloc] initWithTarget:nil interceptor:self];
   super.delegate = (id<UICollectionViewDelegate>)_proxyDelegate;
 
@@ -362,6 +369,63 @@ static BOOL _isInterceptedSelector(SEL sel)
 }
 
 
+#pragma mark -
+#pragma mark Batch Fetching
+
+- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
+{
+  [self handleBatchFetchScrollingToOffset:*targetContentOffset];
+
+  if ([_asyncDelegate respondsToSelector:@selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)]) {
+    [_asyncDelegate scrollViewWillEndDragging:scrollView withVelocity:velocity targetContentOffset:targetContentOffset];
+  }
+}
+
+- (BOOL)shouldFetchBatch
+{
+  if ([self.asyncDelegate respondsToSelector:@selector(shouldBatchFetchForCollectionView:)]) {
+    return [self.asyncDelegate shouldBatchFetchForCollectionView:self];
+  } else {
+    return YES;
+  }
+}
+
+- (void)handleBatchFetchScrollingToOffset:(CGPoint)targetOffset
+{
+  ASDisplayNodeAssert(_batchContext != nil, @"Batch context should exist");
+
+  // Bail if we are already fetching, the delegate doesn't care, or we're told not to fetch
+  if ([_batchContext isFetching] ||
+      ![self.asyncDelegate respondsToSelector:@selector(collectionView:beginBatchFetchingWithContext:)] ||
+      ![self shouldFetchBatch]) {
+    return;
+  }
+
+  ASScrollDirection scrollDirection = [self scrollDirection];
+  CGFloat viewSize, offset, contentSize;
+
+  if (scrollDirection == ASScrollDirectionUp) {
+    viewSize = CGRectGetHeight(self.bounds);
+    offset = targetOffset.y;
+    contentSize = self.contentSize.height;
+  } else { // horizontal
+    viewSize = CGRectGetWidth(self.bounds);
+    offset = targetOffset.x;
+    contentSize = self.contentSize.width;
+  }
+
+  CGFloat triggerDistance = viewSize * _leadingScreensForBatching;
+
+  // Determine if the offset that we are headed to is within the number of screens we have defined
+  // ASCollectionView supports tail loading only currently, hence the check against Up and Left
+  BOOL supportedBatchScrollDirection = scrollDirection == ASScrollDirectionUp || ASScrollDirectionLeft;
+  if (supportedBatchScrollDirection && contentSize - (viewSize + offset) <= triggerDistance) {
+    [_batchContext beginBatchFetching];
+    [self.asyncDelegate collectionView:self beginBatchFetchingWithContext:_batchContext];
+  }
+}
+
+
 #pragma mark - ASDataControllerSource
 
 - (ASCellNode *)dataController:(ASDataController *)dataController nodeAtIndexPath:(NSIndexPath *)indexPath

AsyncDisplayKit/ASTableView.h

@@ -64,7 +64,7 @@
 - (instancetype)initWithFrame:(CGRect)frame style:(UITableViewStyle)style asyncDataFetching:(BOOL)asyncDataFetchingEnabled;
 
 /**
- * The number of screens left to scroll before the delegate -tableView:shouldBeginBatchFetchingWithContext: is called.
+ * The number of screens left to scroll before the delegate -tableView:beginBatchFetchingWithContext: is called.
  *
  * Defaults to one screenful.
  */

AsyncDisplayKit/ASTableView.mm

@@ -401,6 +401,8 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 - (void)handleBatchFetchScrollingToOffset:(CGPoint)targetOffset
 {
+  ASDisplayNodeAssert(_batchContext != nil, @"Batch context should exist");
+
   // Bail if we are already fetching, the delegate doesn't care, or we're told not to fetch
   if ([_batchContext isFetching] ||
       ![self.asyncDelegate respondsToSelector:@selector(tableView:beginBatchFetchingWithContext:)] ||

examples/ASCollectionView/Sample/ViewController.m

@@ -65,7 +65,7 @@
 
 - (ASCellNode *)collectionView:(ASCollectionView *)collectionView nodeForItemAtIndexPath:(NSIndexPath *)indexPath
 {
-  NSString *text = [NSString stringWithFormat:@"[%ld.%ld] says hi", indexPath.section, indexPath.item];
+  NSString *text = [NSString stringWithFormat:@"[%zd.%zd] says hi", indexPath.section, indexPath.item];
   ASTextCellNode *node = [[ASTextCellNode alloc] init];
   node.text = text;
   node.backgroundColor = [UIColor lightGrayColor];
@@ -78,13 +78,21 @@
   return 300;
 }
 
-- (void)collectionViewLockDataSource:(ASCollectionView *)collectionView {
+- (void)collectionViewLockDataSource:(ASCollectionView *)collectionView
+{
   // lock the data source
   // The data source should not be change until it is unlocked.
 }
 
-- (void)collectionViewUnlockDataSource:(ASCollectionView *)collectionView {
+- (void)collectionViewUnlockDataSource:(ASCollectionView *)collectionView
+{
   // unlock the data source to enable data source updating.
 }
 
+- (void)collectionView:(UICollectionView *)collectionView beginBatchFetchingWithContext:(ASBatchContext *)context
+{
+  NSLog(@"fetch additional content");
+  [context completeBatchFetching:YES];
+}
+
 @end