Mobile Feature Development Skill

Use this skill when working on React Native features in apps/mobile/.

Critical React Native Safety Patterns

Boolean Rendering Safety

NEVER use truthy checks with numbers in JSX - React Native renders 0 as literal text:

// ❌ DANGEROUS - renders '0' when count is 0
{count && <Text>{count} items</Text>}

// ✅ SAFE - explicit null check
{count != null && <Text>{count} items</Text>}

// ✅ SAFE - hide zeros
{count > 0 && <Text>{count} items</Text>}

Why: {0 && <Component>} causes "Text strings must be rendered within a component" error.

Always Check For:

• Number conditionals: Replace {number && ...} with {number > 0 && ...} or {number != null && ...}
• Array conditionals: Use {array.length > 0 && ...} not {array.length && ...}
• Optional chains: Use {value?.property != null && ...} not {value?.property && ...}

Internationalization Requirements

ALL text must use translations - no hardcoded strings:

// ✅ REQUIRED
import { useTranslation } from '@hounii/i18n';
const { t } = useTranslation('mobile');

<Text>{t('screen.title')}</Text>

// ❌ FORBIDDEN - no fallback pattern (masks missing keys)
<Text>{t('screen.title') || 'Default'}</Text>

// ❌ FORBIDDEN - no hardcoded strings
<Text>Screen Title</Text>

Translation File Structure:

• Location: packages/i18n/translations/
• Namespaces: mobile.json, common.json
• Languages: en/, fr/, de/, ar/

Tamagui UI Components

Always use Tamagui components from @hounii/ui:

import { Button, Text, View } from '@hounii/ui';

// Use design tokens, not hardcoded values
<View backgroundColor="$background" padding="$4">
  <Text color="$color" fontSize="$5">{t('title')}</Text>
</View>

Feature-Driven Structure

Organize by feature in apps/mobile/features/:

features/
├── auth/
│   ├── screens/
│   ├── components/
│   ├── hooks/
│   └── index.ts
└── profile/
    ├── screens/
    ├── components/
    ├── hooks/
    └── index.ts

State Management

Use Zustand stores from @hounii/lib:

import { useUserStore } from '@hounii/lib/stores';

// Persisted stores MUST have version + migrate
import { create } from 'zustand';
import { persist } from 'zustand/middleware';

export const useFeatureStore = create<FeatureState>()(
  persist(
    (set) => ({
      // state
    }),
    {
      name: 'feature-store',
      version: 1,
      migrate: (persistedState: any, version: number) => {
        if (version === 0) {
          // Migration logic
        }
        return persistedState as FeatureState;
      },
    }
  )
);

Solito Universal Navigation

CRITICAL: Use Solito for navigation (not Expo Router directly). This enables code sharing with web.

// ✅ CORRECT - Solito Link (works on mobile + web)
import { Link } from 'solito/link';

<Link href="/profile">
  <Text>Go to Profile</Text>
</Link>

// ✅ CORRECT - Solito Router (works on mobile + web)
import { useRouter } from 'solito/router';

const router = useRouter();
router.push('/profile');
router.replace('/login');
router.push({ pathname: '/post/[id]', params: { id: '123' } });

// ❌ WRONG - Don't use Expo Router directly
import { router } from 'expo-router'; // Breaks web compatibility

Route Files vs. Screens

CRITICAL: Route files (app/) should ONLY handle routing. All screens live in features/.

// ✅ CORRECT - Route file (apps/mobile/app/(tabs)/index.tsx)
import { HomeScreen } from '@/features/home';
export default HomeScreen;

// ✅ CORRECT - Screen file (apps/mobile/features/home/screens/HomeScreen.tsx)
export function HomeScreen() {
  return (
    <YStack>
      <Text>{t('home.title')}</Text>
    </YStack>
  );
}

// ❌ WRONG - Don't put screen logic in route file
export default function Home() {
  // This logic belongs in features/home/screens/HomeScreen.tsx
  return <YStack>...</YStack>;
}

Development Checklist

When creating a new mobile feature:

1. Safety Patterns

   • All number conditionals use explicit checks (> 0 or != null)
   • No truthy checks with potentially falsy values

2. Internationalization

   • All text uses t() from @hounii/i18n
   • Translation keys added to packages/i18n/translations/
   • No hardcoded strings or fallback patterns

3. UI Components

   • Using Tamagui components from @hounii/ui
   • Using design tokens (e.g., $background, $4) not hardcoded values
   • Dark mode compatibility verified

4. Feature Organization

   • Code in appropriate features/ directory
   • Exports through feature index.ts
   • Shared logic extracted to hooks

5. State Management

   • Using Zustand stores from @hounii/lib
   • Persisted stores have version and migrate functions

6. Type Safety

   • TypeScript types defined
   • No any types without justification
   • Props interfaces exported

7. Navigation

   • Routes defined in app/ directory (routing ONLY)
   • Screens in features/ directory (logic + UI)
   • Using Solito's Link and useRouter (not Expo Router directly)

Before Requesting Commit

1. Run quality gates: pnpm lint && pnpm type-check
2. Provide user with testing instructions:
   • Which screen/feature to test
   • Expected behavior
   • Edge cases to verify (e.g., when count is 0)
3. WAIT for explicit user approval - never commit without confirmation

Common Pitfalls

• Platform-specific code: Use Platform.OS checks or .ios.tsx/.android.tsx files
• Async storage: Use @hounii/lib/storage wrapper, not raw AsyncStorage
• Images: Use expo-image not react-native Image component
• Icons: Use @tamagui/lucide-icons from @hounii/ui

References

• Main config: CLAUDE.md
• Mobile app: apps/mobile/
• UI package: packages/ui/
• i18n package: packages/i18n/