From bf38cf1be98f2d71f77cbc7913387cce4c1acab3 Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Wed, 17 Jul 2019 11:13:27 -0700
Subject: [PATCH] Fabric: Additional checks for _eventEmitter being null in
 ScrollView

Summary:
I finally convinced that we need to add this everywhere.
iOS internals can call those methods at any moment (which is happening in coming diffs), so we cannot predict `_eventEmitter` being not null.

Reviewed By: mdvacca

Differential Revision: D16296052

fbshipit-source-id: 34447c2b5af4117d75930d68593d60bace119bbd
---
 .../ScrollView/RCTScrollViewComponentView.mm  | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm b/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm
index 7dab050fc1a..90502189558 100644
--- a/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm
+++ b/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm
@@ -169,16 +169,28 @@ using namespace facebook::react;
 
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onScroll([self _scrollViewMetrics]);
 }
 
 - (void)scrollViewDidZoom:(UIScrollView *)scrollView
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onScroll([self _scrollViewMetrics]);
 }
 
 - (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onScrollBeginDrag([self _scrollViewMetrics]);
 }
 
@@ -186,34 +198,58 @@ using namespace facebook::react;
                      withVelocity:(CGPoint)velocity
               targetContentOffset:(inout CGPoint *)targetContentOffset
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onScrollEndDrag([self _scrollViewMetrics]);
 }
 
 - (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)
       ->onMomentumScrollBegin([self _scrollViewMetrics]);
 }
 
 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onMomentumScrollEnd([self _scrollViewMetrics]);
   [self _updateStateWithContentOffset];
 }
 
 - (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onMomentumScrollEnd([self _scrollViewMetrics]);
   [self _updateStateWithContentOffset];
 }
 
 - (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(nullable UIView *)view
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onScrollBeginDrag([self _scrollViewMetrics]);
 }
 
 - (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(nullable UIView *)view atScale:(CGFloat)scale
 {
+  if (!_eventEmitter) {
+    return;
+  }
+
   std::static_pointer_cast<const ScrollViewEventEmitter>(_eventEmitter)->onScrollEndDrag([self _scrollViewMetrics]);
   [self _updateStateWithContentOffset];
 }