Added addChildren() function as a more-optimal replacement for manageChildren for common use cases.

Reviewed By: jspahrsummers

Differential Revision: D2707930

fb-gh-sync-id: c44219bf9af943cad5b57f370656c1bcac732cd9

Libraries/ReactNative/ReactNativeBaseComponent.js

@@ -104,11 +104,11 @@ ReactNativeBaseComponent.Mixin = {
     // no children - let's avoid calling out to the native bridge for a large
     // portion of the children.
     if (mountImages.length) {
-      var indexes = cachedIndexArray(mountImages.length);
+      
       // TODO: Pool these per platform view class. Reusing the `mountImages`
       // array would likely be a jit deopt.
       var createdTags = [];
-      for (var i = 0; i < mountImages.length; i++) {
+      for (var i = 0, l = mountImages.length; i < l; i++) {
         var mountImage = mountImages[i];
         var childTag = mountImage.tag;
         var childID = mountImage.rootNodeID;
@@ -122,8 +122,15 @@ ReactNativeBaseComponent.Mixin = {
         );
         createdTags[i] = mountImage.tag;
       }
-      UIManager
-        .manageChildren(containerTag, null, null, createdTags, indexes, null);
+      
+      // Fast path for iOS
+      if (UIManager.addChildren) {
+        UIManager.addChildren(containerTag, createdTags);
+        return; 
+      }
+      
+      var indexes = cachedIndexArray(mountImages.length);
+      UIManager.manageChildren(containerTag, null, null, createdTags, indexes, null);
     }
   },
 

Libraries/ReactNative/ReactNativeDOMIDOperations.js

@@ -53,6 +53,7 @@ var dangerouslyProcessChildrenUpdates = function(childrenUpdates, markupList) {
       (updates.addChildTags || (updates.addChildTags = [])).push(tag);
     }
   }
+  
   // Note this enumeration order will be different on V8!  Move `byContainerTag`
   // to a sparse array as soon as we confirm there are not horrible perf
   // penalties.

Libraries/ReactNative/ReactNativeMount.js

@@ -188,6 +188,16 @@ var ReactNativeMount = {
         mountImage.rootNodeID,
         mountImage.tag
       );
+      
+      // Fast path for iOS
+      if (UIManager.addChildren) {
+        UIManager.addChildren(
+          ReactNativeTagHandles.mostRecentMountedNodeHandleForRootNodeID(containerID),
+          [mountImage.tag]
+        );
+        return;
+      }
+      
       var addChildTags = [mountImage.tag];
       var addAtIndices = [0];
       UIManager.manageChildren(

React/Modules/RCTUIManager.m

@@ -720,6 +720,33 @@ RCT_EXPORT_METHOD(replaceExistingNonRootView:(nonnull NSNumber *)reactTag
         removeAtIndices:removeAtIndices];
 }
 
+RCT_EXPORT_METHOD(addChildren:(nonnull NSNumber *)containerTag
+                  reactTags:(NSNumberArray *)reactTags)
+{
+  RCTAddChildren(containerTag, reactTags,
+                 (NSDictionary<NSNumber *, id<RCTComponent>> *)_shadowViewRegistry);
+
+  [self addUIBlock:^(__unused RCTUIManager *uiManager, NSDictionary<NSNumber *, UIView *> *viewRegistry){
+
+    RCTAddChildren(containerTag, reactTags,
+                   (NSDictionary<NSNumber *, id<RCTComponent>> *)viewRegistry);
+  }];
+}
+
+static void RCTAddChildren(NSNumber *containerTag,
+                           NSArray<NSNumber *> *reactTags,
+                           NSDictionary<NSNumber *, id<RCTComponent>> *registry)
+{
+  id<RCTComponent> container = registry[containerTag];
+  NSInteger index = [container reactSubviews].count;
+  for (NSNumber *reactTag in reactTags) {
+    id<RCTComponent> view = registry[reactTag];
+    if (view) {
+      [container insertReactSubview:view atIndex:index++];
+    }
+  }
+}
+
 RCT_EXPORT_METHOD(manageChildren:(nonnull NSNumber *)containerReactTag
                   moveFromIndices:(NSNumberArray *)moveFromIndices
                   moveToIndices:(NSNumberArray *)moveToIndices
@@ -754,39 +781,57 @@ RCT_EXPORT_METHOD(manageChildren:(nonnull NSNumber *)containerReactTag
         removeAtIndices:(NSArray<NSNumber *> *)removeAtIndices
                registry:(NSMutableDictionary<NSNumber *, id<RCTComponent>> *)registry
 {
+  RCTAssert(moveFromIndices.count == moveToIndices.count,
+            @"moveFromIndices had size %tu, moveToIndices had size %tu",
+            moveFromIndices.count, moveToIndices.count);
+
+  RCTAssert(addChildReactTags.count == addAtIndices.count,
+            @"addChildReactTags had size %tu, addAtIndices had size %tu",
+            addChildReactTags.count, addAtIndices.count);
+
   id<RCTComponent> container = registry[containerReactTag];
-  RCTAssert(moveFromIndices.count == moveToIndices.count, @"moveFromIndices had size %tu, moveToIndices had size %tu", moveFromIndices.count, moveToIndices.count);
-  RCTAssert(addChildReactTags.count == addAtIndices.count, @"there should be at least one React child to add");
+  NSArray<id<RCTComponent>> *views = [container reactSubviews];
 
-  // Removes (both permanent and temporary moves) are using "before" indices
-  NSArray<id<RCTComponent>> *permanentlyRemovedChildren =
-    [self _childrenToRemoveFromContainer:container atIndices:removeAtIndices];
-  NSArray<id<RCTComponent>> *temporarilyRemovedChildren =
-    [self _childrenToRemoveFromContainer:container atIndices:moveFromIndices];
-  [self _removeChildren:permanentlyRemovedChildren fromContainer:container];
-  [self _removeChildren:temporarilyRemovedChildren fromContainer:container];
-
-  [self _purgeChildren:permanentlyRemovedChildren fromRegistry:registry];
-
-  // TODO (#5906496): optimize all these loops - constantly calling array.count is not efficient
-
-  // Figure out what to insert - merge temporary inserts and adds
-  NSMutableDictionary *destinationsToChildrenToAdd = [NSMutableDictionary dictionary];
-  for (NSInteger index = 0, length = temporarilyRemovedChildren.count; index < length; index++) {
-    destinationsToChildrenToAdd[moveToIndices[index]] = temporarilyRemovedChildren[index];
+  // Get indices to insert/remove
+  NSUInteger purgeCount = removeAtIndices.count;
+  NSUInteger moveCount = moveFromIndices.count;
+  NSUInteger insertCount = addAtIndices.count;
+  NSUInteger removeCount = purgeCount + moveCount;
+  NSMutableArray<id<RCTComponent>> *toRemove = removeCount ? [NSMutableArray new] : nil;
+  NSMutableDictionary *toInsert = insertCount ? [NSMutableDictionary new] : nil;
+  for (NSNumber *index in removeAtIndices) {
+    id<RCTComponent> view = views[index.integerValue];
+    [toRemove addObject:view];
+    RCTTraverseViewNodes(registry[view.reactTag], ^(id<RCTComponent> subview) {
+      RCTAssert(![subview isReactRootView], @"Root views should not be unregistered");
+      if ([subview conformsToProtocol:@protocol(RCTInvalidating)]) {
+        [(id<RCTInvalidating>)subview invalidate];
       }
-  for (NSInteger index = 0, length = addAtIndices.count; index < length; index++) {
-    id<RCTComponent> view = registry[addChildReactTags[index]];
-    if (view) {
-      destinationsToChildrenToAdd[addAtIndices[index]] = view;
+      [registry removeObjectForKey:subview.reactTag];
+      [_bridgeTransactionListeners removeObject:subview];
+    });
   }
+  NSInteger i = 0;
+  for (NSNumber *index in moveFromIndices) {
+    id<RCTComponent> view = views[index.integerValue];
+    [toRemove addObject:view];
+    toInsert[moveToIndices[i]] = view;
+    i++;
+  }
+  i = 0;
+  for (NSNumber *reactTag in addChildReactTags) {
+    toInsert[addAtIndices[i]] = registry[reactTag];
+    i++;
   }
 
-  NSArray<NSNumber *> *sortedIndices =
-    [destinationsToChildrenToAdd.allKeys sortedArrayUsingSelector:@selector(compare:)];
-  for (NSNumber *reactIndex in sortedIndices) {
-    [container insertReactSubview:destinationsToChildrenToAdd[reactIndex]
-                          atIndex:reactIndex.integerValue];
+  // Remove old views
+  for (id<RCTComponent> view in toRemove) {
+    [container removeReactSubview:view];
+  }
+
+  // Insert new views in ascending order
+  for (NSNumber *index in [toInsert.allKeys sortedArrayUsingSelector:@selector(compare:)]) {
+    [container insertReactSubview:toInsert[index] atIndex:index.integerValue];
   }
 }