React Native Development Patterns

Quick Guide: Build cross-platform mobile apps with React Native's New Architecture (default since 0.76). Use FlashList for performant lists (or FlatList with proper optimization). Use type-safe navigation hooks with static or dynamic API. Keep components small, memoize callbacks passed to lists, and test on both platforms from day one.

<critical_requirements>

CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering, import type, named constants)

(You MUST use FlashList (preferred) or FlatList for lists with more than 20 items - NEVER ScrollView with .map() for long lists)

(You MUST memoize renderItem callbacks and use stable keyExtractor functions - avoid key props on FlashList items as it breaks recycling)

(You MUST use react-native-safe-area-context for safe areas - React Native's built-in SafeAreaView is deprecated in 0.81+ and will be removed)

(You MUST test on BOTH iOS AND Android from day one - platform differences cause bugs)

(You MUST use Platform.select() or platform-specific files for platform differences - shadows, fonts, and feedback differ)

(You MUST be aware the New Architecture is enabled by default since React Native 0.76 - Fabric, TurboModules, and bridgeless mode)

</critical_requirements>

Auto-detection: React Native, react-native, React Navigation, @react-navigation, StyleSheet, FlatList, FlashList, ScrollView, View, Text, Pressable, TouchableOpacity, Platform.OS, Platform.select, SafeAreaView, KeyboardAvoidingView, Reanimated, Gesture Handler, TurboModules, Fabric, JSI, New Architecture

When to use:

• Building cross-platform iOS and Android mobile applications
• Creating native mobile UIs with React patterns
• Implementing mobile navigation with stack, tab, or drawer patterns
• Optimizing list performance with FlashList/FlatList and virtualization
• Adding gestures and animations with Reanimated 4
• Handling platform-specific code for iOS vs Android differences
• Working with React Native's New Architecture (Fabric, TurboModules, JSI)

Key patterns covered:

• New Architecture fundamentals (Fabric, TurboModules, JSI, bridgeless mode)
• Component architecture with accessibility props and platform-specific patterns
• React Navigation 7+ with type-safe hooks, static API, and auth flows
• FlashList/FlatList optimization with memoization and cell recycling
• Platform-specific code with Platform.select and file extensions
• Safe area and keyboard handling
• React 19 features (React Native 0.78+): useOptimistic, use, ref as props

When NOT to use:

• Web-only React applications (use standard React patterns)
• React Native Web hybrid apps (requires additional considerations)
• Flutter, Swift, or Kotlin native development

Detailed Resources:

• examples/core.md - Component architecture, compound components
• examples/navigation.md - Type-safe navigation, auth flows, deep linking
• examples/styling.md - StyleSheet, design tokens, theming, responsive styling
• examples/performance.md - FlashList, FlatList optimization, memoization
• reference.md - Decision frameworks, checklists, CLI commands

Philosophy

React Native enables building native mobile apps using React patterns. The key insight is that mobile has different constraints than web: performance matters more, platform conventions differ, and users expect native feel.

Core principles:

1. New Architecture first - React Native 0.76+ uses the New Architecture by default (Fabric, TurboModules, JSI, bridgeless mode)
2. Platform-first thinking - iOS and Android have different UX conventions (haptics, ripples, navigation patterns)
3. Performance by default - Mobile devices are constrained; use FlashList/FlatList, memoize callbacks, avoid inline styles
4. Native feel matters - Use native components, proper keyboard handling, safe area insets
5. Type safety prevents bugs - Type navigation params, props, and native module interfaces
6. Test both platforms early - Platform bugs compound over time; test daily on both

New Architecture (React Native 0.76+):

The New Architecture removes the legacy bridge and provides:

• Fabric - Modern rendering engine with synchronous layout effects
• TurboModules - Lazy-loaded native modules with type-safe interfaces
• JSI (JavaScript Interface) - Direct synchronous JS-to-native calls without serialization
• Bridgeless Mode - Complete removal of the async bridge for better performance

Performance improvements with New Architecture: ~15ms faster app startup (~8% improvement), ~3.8MB smaller app size (20% reduction), ~15x faster Metro resolver, ~4x faster warm builds.

Mental model:

React Native is NOT "write once, run anywhere" - it's "learn once, write anywhere." Expect to write some platform-specific code. The shared codebase is typically 80-95%, not 100%.

Core Patterns

Pattern 1: Component Architecture

Build components with TypeScript, accessibility props, and platform awareness. Key concerns: use Pressable over TouchableOpacity, include accessibilityRole/accessibilityState, use testID for E2E tests, and memoize styles with useMemo.

// Key pattern: accessibility + testID + memoized styles
<Pressable
  ref={ref}
  style={buttonStyle}
  onPress={handlePress}
  disabled={disabled}
  testID={testID}
  accessibilityRole="button"
  accessibilityState={{ disabled }}
>
  <Text style={styles.text}>{children}</Text>
</Pressable>

Why good: accessibilityRole/State for screen readers, testID for E2E, Pressable supports android_ripple unlike TouchableOpacity

See examples/core.md for full component with forwardRef, variants, and loading state.

Pattern 2: Safe Area and Keyboard Handling

Handle device notches, status bars, and keyboard properly. Use react-native-safe-area-context (RN's built-in SafeAreaView is deprecated in 0.81+).

import { SafeAreaView, useSafeAreaInsets } from "react-native-safe-area-context";

// Screen wrapper with safe areas
<SafeAreaView style={{ flex: 1 }} edges={["top", "bottom"]}>
  {children}
</SafeAreaView>

// Keyboard handling for forms
<KeyboardAvoidingView
  style={{ flex: 1 }}
  behavior={Platform.OS === "ios" ? "padding" : "height"}
  keyboardVerticalOffset={Platform.select({ ios: HEADER_HEIGHT, android: 0 })}
>
  <ScrollView keyboardShouldPersistTaps="handled">
    <FormContent />
  </ScrollView>
</KeyboardAvoidingView>

Why good: SafeAreaView handles notches/Dynamic Island, KeyboardAvoidingView prevents keyboard overlap, Platform.select handles iOS/Android differences

Pattern 3: Platform-Specific Code

Handle iOS and Android differences with Platform.select for small differences, separate files (.ios.tsx/.android.tsx) for significant divergence.

// Platform.select for shadows (iOS shadow props ignored on Android)
const styles = StyleSheet.create({
  card: {
    ...Platform.select({
      ios: {
        shadowColor: "#000",
        shadowOffset: { width: 0, height: 2 },
        shadowOpacity: 0.1,
        shadowRadius: 4,
      },
      android: { elevation: 4 },
    }),
  },
  text: {
    fontWeight: Platform.select({ ios: "600", android: "bold" }),
  },
});

Why good: iOS shadow props are completely ignored on Android, fontWeight 100-900 unreliable on Android

For platform-specific file splitting with haptics, see examples/core.md.

Pattern 4: FlashList and FlatList Optimization

Use FlashList for performant lists (cell recycling, 50% less blank area). FlashList v2 is New Architecture only. Always memoize renderItem and keyExtractor. Never add key prop