From dcb526bdc7fb05bac419f4162c0b4aca98bf6336 Mon Sep 17 00:00:00 2001
From: Adam McDonald <adam.mcdonald@rover.com>
Date: Fri, 17 Jul 2026 11:56:22 -0700
Subject: [PATCH] fix(ios): skip programmatic selectRow while user is scrolling

On the New Architecture (Fabric), a controlled Picker can crash with
EXC_BAD_ACCESS during a fast fling. Every committed value flows through
-setSelectedIndex:, which calls -selectRow:animated:. Mid-gesture, lagging
React state echoes back a stale index that re-drives the live wheel,
re-entering UIPickerView's suspended update cycle during UIKit hit-testing.

Add an -isUserScrolling helper that inspects the picker's backing
UIScrollView(s) (isTracking/isDragging/isDecelerating) and bail out of
-setSelectedIndex: while the user is actively manipulating the wheel.
-didSelectRow: already keeps the internal index accurate, so idle
programmatic resets continue to work.
---
 ios/RNCPicker.mm | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/ios/RNCPicker.mm b/ios/RNCPicker.mm
index 9a9405646..388344581 100644
--- a/ios/RNCPicker.mm
+++ b/ios/RNCPicker.mm
@@ -45,8 +45,37 @@ - (void)setItems:(NSArray<NSDictionary *> *)items
   [self setNeedsLayout];
 }
 
+- (BOOL)isUserScrolling
+{
+  // UIPickerView drives each wheel with an internal UIScrollView. Walk the
+  // subview tree and report whether any of them is currently being touched or
+  // is still settling after a fling.
+  NSMutableArray<UIView *> *stack = [NSMutableArray arrayWithArray:self.subviews];
+  while (stack.count > 0) {
+    UIView *view = stack.lastObject;
+    [stack removeLastObject];
+    if ([view isKindOfClass:[UIScrollView class]]) {
+      UIScrollView *scrollView = (UIScrollView *)view;
+      if (scrollView.isTracking || scrollView.isDragging || scrollView.isDecelerating) {
+        return YES;
+      }
+    }
+    [stack addObjectsFromArray:view.subviews];
+  }
+  return NO;
+}
+
 - (void)setSelectedIndex:(NSInteger)selectedIndex
 {
+  // While the user is physically manipulating the wheel, a controlled parent can
+  // echo back a stale selected index and re-drive selectRow: mid-gesture. Under
+  // the New Architecture this re-enters UIPickerView's suspended update cycle
+  // during hit-testing and crashes. didSelectRow: already keeps the internal
+  // index accurate, so skipping the programmatic update here is safe; idle resets
+  // still apply.
+  if ([self isUserScrolling]) {
+    return;
+  }
   if (_selectedIndex != selectedIndex) {
     BOOL animated = _selectedIndex != NSNotFound; // Don't animate the initial value
     _selectedIndex = selectedIndex;