renderBottomAccessoryView crashes on iOS 26: RCTBottomAccessoryComponentView does not initialize _props in its constructor

從ios/RCTBottomAccessoryComponentView.mm開始，將initWithFrame:的設定與RCTTabViewComponentView.mm比較，issue指出後者是可正常運作的範例。將現有的defaultProps指派給_props，接著在 iOS 26 的 Debug 模式下使用renderBottomAccessoryView建置並執行提供的範例；當配件視圖掛載時沒有觸發 assertion，並顯示在分頁列上方，即表示完成。

Before submitting a new issue

• I tested using the latest version of the library, as the bug might be already fixed.
• I tested using a supported version of react native.
• I checked for possible duplicate issues, with possible answers.

Bug summary

Description

Using the iOS 26 bottom accessory feature (renderBottomAccessoryView) crashes the app
immediately on first render:

Thread 1: "`RCTViewComponentView` subclasses (and `RCTBottomAccessoryComponentView`
particularly) must setup `_props` instance variable with a default value in the constructor."

Removing renderBottomAccessoryView makes the app run normally, so the crash is specific to
the accessory component view.

Library version

1.5.0

Environment info

info Fetching system and libraries information...
System:
  OS: macOS 26.5.2
  CPU: (10) arm64 Apple M4
  Memory: 87.67 MB / 24.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 24.18.0
    path: /var/folders/lt/t4vyv6s110d1p6mg8_fwsd9h0000gn/T/yarn--1793087516853-0.2936365526559257/node
  Yarn:
    version: 1.22.22
    path: /var/folders/lt/t4vyv6s110d1p6mg8_fwsd9h0000gn/T/yarn--1793087516853-0.2936365526559257/yarn
  npm:
    version: 11.16.0
    path: /Users/munitcat/.vfox/sdks/nodejs/bin/npm
  Watchman:
    version: 2026.07.20.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.17.0
    path: /opt/homebrew/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.5
      - iOS 26.5
      - macOS 26.5
      - tvOS 26.5
      - visionOS 26.5
      - watchOS 26.5
  Android SDK: Not Found
IDEs:
  Android Studio: 2026.1 AI-261.25134.95.2612.15822958
  Xcode:
    version: 26.6/17F113
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.18
    path: /usr/bin/javac
  Ruby:
    version: 4.0.6
    path: /opt/homebrew/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.2.0
    wanted: 20.2.0
  react:
    installed: 19.3.0
    wanted: 19.3.0
  react-native:
    installed: 0.88.0
    wanted: 0.88.0
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Steps to reproduce

Root cause

ios/RCTBottomAccessoryComponentView.mm — initWithFrame: creates defaultProps but never
assigns it to the _props ivar:

- (instancetype)initWithFrame:(CGRect)frame
{
  if (self = [super initWithFrame:frame]) {
    static const auto defaultProps = std::make_shared<const BottomAccessoryViewProps>();
    if (@available(iOS 26.0, *)) {          // <-- defaultProps is never used
      bottomAccessoryProvider = [[BottomAccessoryProvider alloc] initWithDelegate:self];
    }
  }
  return self;
}

RCTViewComponentView (react-native 0.88.0,
React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm:137) initializes the ivar
with plain ViewProps:

_props = ViewShadowNode::defaultSharedProps();

and then asserts in updateProps:oldProps: (line 333–346) that every subclass replaces it with
its own props type:

RCTAssert(
    propsRawPtr &&
        ([self class] == [RCTViewComponentView class] ||
         typeid(*propsRawPtr).hash_code() != typeid(const ViewProps).hash_code()),
    @"`RCTViewComponentView` subclasses (and `%@` particularly) must setup `_props`"
     " instance variable with a default value in the constructor.",
    NSStringFromClass([self class]));

Because RCTBottomAccessoryComponentView never overrides _props, typeid(*_props) is still
ViewProps and the assertion fires.

For comparison, RCTTabViewComponentView.mm does it correctly in the same constructor:

static const auto defaultProps = std::make_shared<const RNCTabViewProps>();
...
self.contentView = _tabViewProvider;
_props = defaultProps;   // <-- this line is missing in the accessory view

Fix

One line, in ios/RCTBottomAccessoryComponentView.mm:

   if (self = [super initWithFrame:frame]) {
     static const auto defaultProps = std::make_shared<const BottomAccessoryViewProps>();
+    _props = defaultProps;
     if (@available(iOS 26.0, *)) {

This also silences the unused variable 'defaultProps' compiler warning.

Scope / notes

• Only affects builds with the New Architecture, as the file is wrapped in
  #ifdef RCT_NEW_ARCH_ENABLED.
• Only triggered when renderBottomAccessoryView is provided and
  Platform.Version >= 26 — that is the only path where BottomAccessoryView is mounted
  (src/TabView.tsx, around line 522).
• Debug only. The assertion sits inside #ifndef NS_BLOCK_ASSERTIONS, so it is compiled
  out in Release. Release builds don't crash, but the component view keeps running on the
  base ViewProps instead of its own props type.

Workaround

Until a release with the fix is out, apply the patch through patch-package:

npm i -D patch-package
npx patch-package react-native-bottom-tabs

and add "postinstall": "patch-package" to package.json.
The generated patch is attached below.

diff --git a/node_modules/react-native-bottom-tabs/ios/RCTBottomAccessoryComponentView.mm b/node_modules/react-native-bottom-tabs/ios/RCTBottomAccessoryComponentView.mm
--- a/node_modules/react-native-bottom-tabs/ios/RCTBottomAccessoryComponentView.mm
+++ b/node_modules/react-native-bottom-tabs/ios/RCTBottomAccessoryComponentView.mm
@@ -40,6 +40,7 @@ - (instancetype)initWithFrame:(CGRect)frame
 {
   if (self = [super initWithFrame:frame]) {
     static const auto defaultProps = std::make_shared<const BottomAccessoryViewProps>();
+    _props = defaultProps;
     if (@available(iOS 26.0, *)) {
 #if SWIFT_PACKAGE
       bottomAccessoryProvider = RNCCreateBottomAccessoryProvider(self);

Alternatively, simply do not pass renderBottomAccessoryView — the tab bar itself works fine
without it.

Reproducible sample code

## Steps to reproduce


import TabView from 'react-native-bottom-tabs';

const routes = [
  { key: 'home', title: 'Home', focusedIcon: { sfSymbol: 'house.fill' } },
];

<TabView
  navigationState={{ index: 0, routes }}
  renderScene={() => <View />}
  onIndexChange={() => {}}
  renderBottomAccessoryView={() => <View style={{ height: 44 }} />}
/>


Run on an **iOS 26** device or simulator in **Debug**. The app crashes while mounting the  
`BottomAccessoryView` component.Expected

The bottom accessory renders above the tab bar.