ASDataController improvements

- _populateFromDataSourceWithSectionIndexSet doesn't accept a mutanle array but allocate one itself.
- Remove _populateFromEntireDataSourceWithMutableContexts.
- ASIndexedNodeContext executes its block, nil out the block and return the result.

AsyncDisplayKit/Details/ASDataController.mm

@@ -178,9 +178,7 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
       dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
       dispatch_apply(batchCount, queue, ^(size_t i) {
         unsigned long k = j + i;
-        ASIndexedNodeContext *context = contexts[k];
+        ASCellNode *node = [contexts[k] allocateNode];
-        ASCellNodeBlock nodeBlock = context.nodeBlock;
-        ASCellNode *node = nodeBlock();
         ASDisplayNodeAssertNotNil(node, @"Node block created nil node");
         allocatedNodeBuffer[i] = node;
       });
@@ -422,8 +420,8 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
 
     [self accessDataSourceSynchronously:synchronously withBlock:^{
       NSUInteger sectionCount = [_dataSource numberOfSectionsInDataController:self];
-      NSMutableArray<ASIndexedNodeContext *> *contexts = [NSMutableArray array];
+      NSIndexSet *sectionIndexSet = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, sectionCount)];
-      [self _populateFromEntireDataSourceWithMutableContexts:contexts];
+      NSArray<ASIndexedNodeContext *> *contexts = [self _populateFromDataSourceWithSectionIndexSet:sectionIndexSet];
 
       // Allow subclasses to perform setup before going into the edit transaction
       [self prepareForReloadData];
@@ -441,13 +439,12 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
         
         [self willReloadData];
         
-        // Insert each section
+        // Insert empty sections
         NSMutableArray *sections = [NSMutableArray arrayWithCapacity:sectionCount];
         for (int i = 0; i < sectionCount; i++) {
           [sections addObject:[[NSMutableArray alloc] init]];
         }
-        
+        [self _insertSections:sections atIndexSet:sectionIndexSet withAnimationOptions:animationOptions];
-        [self _insertSections:sections atIndexSet:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, sectionCount)] withAnimationOptions:animationOptions];
 
         [self _batchLayoutNodesFromContexts:contexts withAnimationOptions:animationOptions];
 
@@ -494,11 +491,10 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
 
 /**
  * Fetches row contexts for the provided sections from the data source.
- *
- * @discussion Results are stored in the passed mutable arrays.
  */
-- (void)_populateFromDataSourceWithSectionIndexSet:(NSIndexSet *)indexSet mutableContexts:(NSMutableArray<ASIndexedNodeContext *> *)contexts
+- (NSArray<ASIndexedNodeContext *> *)_populateFromDataSourceWithSectionIndexSet:(NSIndexSet *)indexSet
 {
+  NSMutableArray<ASIndexedNodeContext *> *contexts = [NSMutableArray array];
   [indexSet enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
     NSUInteger rowNum = [_dataSource dataController:self rowsInSection:idx];
     NSIndexPath *sectionIndex = [[NSIndexPath alloc] initWithIndex:idx];
@@ -511,31 +507,9 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
                                                           constrainedSize:constrainedSize]];
     }
   }];
+  return contexts;
 }
 
-/**
- * Fetches row contexts for all sections from the data source.
- *
- * @discussion Results are stored in the passed mutable arrays.
- */
-- (void)_populateFromEntireDataSourceWithMutableContexts:(NSMutableArray<ASIndexedNodeContext *> *)contexts
-{
-  NSUInteger sectionNum = [_dataSource numberOfSectionsInDataController:self];
-  for (NSUInteger i = 0; i < sectionNum; i++) {
-    NSIndexPath *sectionIndexPath = [[NSIndexPath alloc] initWithIndex:i];
-    NSUInteger rowNum = [_dataSource dataController:self rowsInSection:i];
-    for (NSUInteger j = 0; j < rowNum; j++) {
-      NSIndexPath *indexPath = [sectionIndexPath indexPathByAddingIndex:j];
-      ASCellNodeBlock nodeBlock = [_dataSource dataController:self nodeBlockAtIndexPath:indexPath];
-      ASSizeRange constrainedSize = [self constrainedSizeForNodeOfKind:ASDataControllerRowNodeKind atIndexPath:indexPath];
-      [contexts addObject:[[ASIndexedNodeContext alloc] initWithNodeBlock:nodeBlock
-                                                                indexPath:indexPath
-                                                          constrainedSize:constrainedSize]];
-    }
-  }
-}
-
-
 #pragma mark - Batching (External API)
 
 - (void)beginUpdates
@@ -617,8 +591,7 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
     [_editingTransactionQueue waitUntilAllOperationsAreFinished];
     
     [self accessDataSourceWithBlock:^{
-      NSMutableArray<ASIndexedNodeContext *> *contexts = [NSMutableArray array];
+      NSArray<ASIndexedNodeContext *> *contexts = [self _populateFromDataSourceWithSectionIndexSet:sections];
-      [self _populateFromDataSourceWithSectionIndexSet:sections mutableContexts:contexts];
 
       [self prepareForInsertSections:sections];
       
@@ -668,8 +641,7 @@ static void *kASSizingQueueContext = &kASSizingQueueContext;
     [_editingTransactionQueue waitUntilAllOperationsAreFinished];
 
     [self accessDataSourceWithBlock:^{
-      NSMutableArray<ASIndexedNodeContext *> *contexts = [NSMutableArray array];
+      NSArray<ASIndexedNodeContext *> *contexts= [self _populateFromDataSourceWithSectionIndexSet:sections];
-      [self _populateFromDataSourceWithSectionIndexSet:sections mutableContexts:contexts];
 
       [self prepareForReloadSections:sections];
       

AsyncDisplayKit/Details/ASIndexedNodeContext.h

@@ -7,11 +7,9 @@
 //
 
 #import <AsyncDisplayKit/ASDataController.h>
-#import <AsyncDisplayKit/ASDimension.h>
 
 @interface ASIndexedNodeContext : NSObject
 
-@property (nonatomic, readonly, strong) ASCellNodeBlock nodeBlock;
 @property (nonatomic, readonly, strong) NSIndexPath *indexPath;
 @property (nonatomic, readonly, assign) ASSizeRange constrainedSize;
 
@@ -19,4 +17,9 @@
                         indexPath:(NSIndexPath *)indexPath
                   constrainedSize:(ASSizeRange)constrainedSize;
 
+/**
+ * Returns a node allocated by executing node block. Node block will be nil out immediately.
+ */
+- (ASCellNode *)allocateNode;
+
 @end

AsyncDisplayKit/Details/ASIndexedNodeContext.m

@@ -8,12 +8,20 @@
 
 #import "ASIndexedNodeContext.h"
 
+@interface ASIndexedNodeContext ()
+
+/// Required node block used to allocate a cell node. Nil after the first execution.
+@property (nonatomic, strong) ASCellNodeBlock nodeBlock;
+
+@end
+
 @implementation ASIndexedNodeContext
 
 - (instancetype)initWithNodeBlock:(ASCellNodeBlock)nodeBlock
                         indexPath:(NSIndexPath *)indexPath
                   constrainedSize:(ASSizeRange)constrainedSize;
 {
+  NSAssert(nodeBlock != nil && indexPath != nil, @"Node block and index path must not be nil");
   self = [super init];
   if (self) {
     _nodeBlock = nodeBlock;
@@ -23,4 +31,12 @@
   return self;
 }
 
+- (ASCellNode *)allocateNode
+{
+  NSAssert(_nodeBlock != nil, @"Node block is gone. Should not execute it more than once");
+  ASCellNode *node = _nodeBlock();
+  _nodeBlock = nil;
+  return node;
+}
+
 @end