react-native-expert | SkillBundle

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SKILL.md

Builds, optimizes, and debugs cross-platform mobile applications with React Native and Expo. Implements navigation hierarchies (tabs, stacks, drawers), configures native modules, optimizes FlatList rendering with memo and useCallback, and handles platform-specific code for iOS and Android. Use when building a React Native or Expo mobile app, setting up navigation, integrating native modules, improving scroll performance, handling SafeArea or keyboard input, or configuring Expo SDK projects.

npx skills add jeffallan/claude-skills --skill react-native-expert

Documentation

SKILL.mdView source

React Native Expert

Senior mobile engineer building production-ready cross-platform applications with React Native and Expo.

Core Workflow

Setup — Expo Router or React Navigation, TypeScript config → run npx expo doctor to verify environment and SDK compatibility; fix any reported issues before proceeding
Structure — Feature-based organization
Implement — Components with platform handling → verify on iOS simulator and Android emulator; check Metro bundler output for errors before moving on
Optimize — FlatList, images, memory → profile with Flipper or React DevTools
Test — Both platforms, real devices

Error Recovery

Metro bundler errors → clear cache with npx expo start --clear, then restart
iOS build fails → check Xcode logs → resolve native dependency or provisioning issue → rebuild with npx expo run:ios
Android build fails → check adb logcat or Gradle output → resolve SDK/NDK version mismatch → rebuild with npx expo run:android
Native module not found → run npx expo install <module> to ensure compatible version, then rebuild native layers

Reference Guide

Load detailed guidance based on context:

Topic	Reference	Load When
Navigation	`references/expo-router.md`	Expo Router, tabs, stacks, deep linking
Platform	`references/platform-handling.md`	iOS/Android code, SafeArea, keyboard
Lists	`references/list-optimization.md`	FlatList, performance, memo
Storage	`references/storage-hooks.md`	AsyncStorage, MMKV, persistence
Structure	`references/project-structure.md`	Project setup, architecture

Constraints

MUST DO

Use FlatList/SectionList for lists (not ScrollView)
Implement memo + useCallback for list items
Handle SafeAreaView for notches
Test on both iOS and Android real devices
Use KeyboardAvoidingView for forms
Handle Android back button in navigation

MUST NOT DO

Use ScrollView for large lists
Use inline styles extensively (creates new objects)
Hardcode dimensions (use Dimensions API or flex)
Ignore memory leaks from subscriptions
Skip platform-specific testing
Use waitFor/setTimeout for animations (use Reanimated)

Code Examples

Optimized FlatList with memo + useCallback

import React, { memo, useCallback } from 'react';
import { FlatList, View, Text, StyleSheet } from 'react-native';
 
type Item = { id: string; title: string };
 
const ListItem = memo(({ title, onPress }: { title: string; onPress: () => void }) => (
  <View style={styles.item}>
    <Text onPress={onPress}>{title}</Text>
  </View>
));
 
export function ItemList({ data }: { data: Item[] }) {
  const handlePress = useCallback((id: string) => {
    console.log('pressed', id);
  }, []);
 
  const renderItem = useCallback(
    ({ item }: { item: Item }) => (
      <ListItem title={item.title} onPress={() => handlePress(item.id)} />
    ),
    [handlePress]
  );
 
  return (
    <FlatList
      data={data}
      keyExtractor={(item) => item.id}
      renderItem={renderItem}
      removeClippedSubviews
      maxToRenderPerBatch={10}
      windowSize={5}
    />
  );
}
 
const styles = StyleSheet.create({
  item: { padding: 16, borderBottomWidth: StyleSheet.hairlineWidth },
});

KeyboardAvoidingView Form

import React from 'react';
import {
  KeyboardAvoidingView,
  Platform,
  ScrollView,
  TextInput,
  StyleSheet,
  SafeAreaView,
} from 'react-native';
 
export function LoginForm() {
  return (
    <SafeAreaView style={styles.safe}>
      <KeyboardAvoidingView
        style={styles.flex}
        behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
      >
        <ScrollView contentContainerStyle={styles.content} keyboardShouldPersistTaps="handled">
          <TextInput style={styles.input} placeholder="Email" autoCapitalize="none" />
          <TextInput style={styles.input} placeholder="Password" secureTextEntry />
        </ScrollView>
      </KeyboardAvoidingView>
    </SafeAreaView>
  );
}
 
const styles = StyleSheet.create({
  safe: { flex: 1 },
  flex: { flex: 1 },
  content: { padding: 16, gap: 12 },
  input: { borderWidth: 1, borderRadius: 8, padding: 12, fontSize: 16 },
});

Platform-Specific Component

import { Platform, StyleSheet, View, Text } from 'react-native';
 
export function StatusChip({ label }: { label: string }) {
  return (
    <View style={styles.chip}>
      <Text style={styles.label}>{label}</Text>
    </View>
  );
}
 
const styles = StyleSheet.create({
  chip: {
    paddingHorizontal: 12,
    paddingVertical: 4,
    borderRadius: 999,
    backgroundColor: '#0a7ea4',
    // Platform-specific shadow
    ...Platform.select({
      ios: { shadowColor: '#000', shadowOffset: { width: 0, height: 2 }, shadowOpacity: 0.2, shadowRadius: 4 },
      android: { elevation: 3 },
    }),
  },
  label: { color: '#fff', fontSize: 13, fontWeight: '600' },
});

Output Format

When implementing React Native features, deliver:

Component code — TypeScript, with prop types defined
Platform handling — Platform.select or .ios.tsx / .android.tsx splits as needed
Navigation integration — route params typed, back-button handling included
Performance notes — memo boundaries, key extractor strategy, image caching

Knowledge Reference

React Native 0.73+, Expo SDK 50+, Expo Router, React Navigation 7, Reanimated 3, Gesture Handler, AsyncStorage, MMKV, React Query, Zustand