Break retain cycle in RCTScrollViewComponentView

Summary: Breaks cycle by making self weak and storing delegates weakly.

Reviewed By: fkgozali

Differential Revision: D16579754

fbshipit-source-id: 17174b0e91898a14a86b8b44677090be3044382d

React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm

@@ -53,8 +53,9 @@ using namespace facebook::react;
     _containerView = [[UIView alloc] initWithFrame:CGRectZero];
     [_scrollView addSubview:_containerView];
 
+    __weak __typeof(self) weakSelf = self;
     _scrollViewDelegateSplitter = [[RNGenericDelegateSplitter alloc] initWithDelegateUpdateBlock:^(id delegate) {
-      self->_scrollView.delegate = delegate;
+      weakSelf.scrollView.delegate = delegate;
     }];
 
     [_scrollViewDelegateSplitter addDelegate:self];

React/Fabric/Utils/RNGenericDelegateSplitter.mm

@@ -8,7 +8,7 @@
 #import "RNGenericDelegateSplitter.h"
 
 @implementation RNGenericDelegateSplitter {
-  NSMutableArray *_delegates;
+  NSHashTable *_delegates;
 }
 
 #pragma mark - Public
@@ -17,7 +17,7 @@
 {
   if (self = [super init]) {
     _delegateUpdateBlock = block;
-    _delegates = [NSMutableArray new];
+    _delegates = [NSHashTable weakObjectsHashTable];
   }
 
   return self;
@@ -44,7 +44,7 @@
     return;
   }
 
-  _delegateUpdateBlock(_delegates.count == 1 ? _delegates.firstObject : self);
+  _delegateUpdateBlock(_delegates.count == 1 ? [_delegates allObjects].firstObject : self);
 }
 
 #pragma mark - Fast Forwarding