Mobile — React Native + Expo

Mobile app only. Do not apply to web-only projects. Verify stack matches PROJECT_RULES.md. Record architecture decisions in docs/ai-dev/.

Initial Setup

npx create-expo-app@latest my-app --template blank-typescript
cd my-app
npx expo install expo-router expo-linking expo-constants
npx expo install nativewind tailwindcss

Directory Structure

app/
├── _layout.tsx           # Root layout (navigation)
├── index.tsx             # Home screen
├── (tabs)/
│   ├── _layout.tsx       # Tab navigator
│   ├── home.tsx
│   └── profile.tsx
├── (auth)/
│   ├── login.tsx
│   └── signup.tsx
└── [id].tsx              # Dynamic route
components/
├── ui/                   # Reusable UI components
└── {feature}/            # Feature-specific components
lib/
├── api.ts                # API client (fetch)
└── storage.ts            # AsyncStorage helpers
types/
└── index.ts              # Shared types

Key Patterns

• One component = max 150 lines. Split if exceeded
• Use RN core components first (View, Text, Pressable, FlatList)
• Props: define with TypeScript interfaces
• State: useState first, Zustand if complex
• HTTP requests: use built-in fetch only. Do NOT install Axios
• Navigation: Expo Router (file-based, like Next.js App Router)

NativeWind Patterns

// Layout
<View className="flex-1 px-4">
  <Text className="text-2xl font-bold text-gray-900 dark:text-white">Title</Text>
</View>

// Card
<View className="bg-white dark:bg-gray-800 rounded-xl p-4 shadow-sm">
  <Text className="text-lg font-semibold">{title}</Text>
</View>

// List
<FlatList
  data={items}
  keyExtractor={(item) => item.id}
  renderItem={({ item }) => <ItemCard item={item} />}
  contentContainerClassName="gap-3 p-4"
/>

Running

npx expo start
# Phone: install "Expo Go" app, scan QR code
# iOS simulator: press "i" | Android emulator: press "a"

Building Screens

1. Create app/{path}.tsx
2. Build in order: layout -> components -> data connection
3. Handle empty, loading, error states
4. Test on Expo Go (scan QR with phone)
5. ESLint pass

Source: ccivlcid/VibeHarness — distributed by TomeVault.