mobile-developer

## Iron Law **FOR FLUTTER WORK — USE `flutter-mobile` SKILL INSTEAD. This skill is for React Native, native Swift/Kotlin, and mobile CI/CD only.** # Mobile Developer Skill ## Disambiguation — Which Skill to Use | Task | Use This Skill | Use flutter-mobile Instead | |------|---------------|---------------------------| | React Native app | YES | No | | Flutter screen/provider/widget | No | YES | | Native Swift/SwiftUI module | YES | No | | Native Kotlin/Compose module | YES | No | | Fastlane lanes / Codemagic pipeline | YES | No | | EAS Update / CodePush OTA | YES | No | | Flutter CI/CD (GitHub Actions, build) | No — use deployment-engineer agent | No | | Detox E2E (React Native) | YES | No | | Maestro E2E (Flutter) | No | YES (via flutter-mobile) | | App Store signing (any) | No | No — use asc-signing-setup skill | ## Capabilities ### 1. React Native (RN 0.74+, New Architecture) New Architecture (Fabric renderer, TurboModules, JSI), Hermes engine, Metro bundler configuration, Flipper debugging, Codegen for typed native modules, and the bridge-free JSI layer for synchronous native calls. ### 2. Expo (SDK 50+) EAS Build for managed and bare workflows, EAS Update for over-the-air JS bundle delivery, development builds with custom native code, config plugins for extending native projects without ejecting. ### 3. Native Integration Swift/SwiftUI platform channel implementations (method channels, event channels), Kotlin/Compose native module authoring, brownfield integration (embedding RN screens in an existing native app or vice versa). ### 4. Architecture Clean Architecture for React Native (data/domain/presentation layers), MVVM with React Query or Zustand, MVI with Redux Toolkit, BLoC pattern adapted for RN, feature-first folder structure mirroring the flutter-mobile convention. ### 5. Performance App startup time reduction (Hermes bytecode, lazy loading), memory leak detection (Flipper Memory Monitor, Instruments, Android Profiler), battery impact analysis, FlatList/FlashList virtualization, Reanimated 3 for 60fps UI-thread animations, InteractionManager for deferred heavy work. ### 6. Data Management Realm for complex relational offline data, WatermelonDB for high-performance sync, MMKV for fast key-value storage, offline-first sync patterns with conflict resolution (last-write-wins, CRDT), background sync with WorkManager (Android) and BGTaskScheduler (iOS). ### 7. Mobile CI/CD Fastlane lanes (match for code signing, gym for builds, pilot/deliver for distribution), Codemagic YAML workflows, Bitrise pipelines, GitHub Actions with mobile-specific caching (CocoaPods, Gradle), CodePush for hotfix OTA, EAS Update for Expo-managed OTA. ### 8. Testing Jest unit tests with `@testing-library/react-native`, Detox for black-box E2E on device/emulator, Maestro for declarative E2E (RN and native), XCTest for Swift unit tests, Firebase Test Lab and Bitrise device farm for multi-device coverage. ### 9. Security OWASP MASVS compliance (MASVS-STORAGE, MASVS-CRYPTO, MASVS-NETWORK, MASVS-AUTH), `react-native-keychain` / `expo-secure-store` for credential storage, certificate pinning via `react-native-ssl-pinning` or TrustKit (iOS), RASP (Runtime Application Self-Protection), jailbreak/root detection. ## Quick Reference — React Native Setup ```bash # New React Native project (Expo recommended for new projects) npx create-expo-app MyApp --template blank-typescript cd MyApp # Core RN dependencies npx expo install expo-router react-native-screens react-native-safe-area-context # EAS CLI for builds and OTA npm install -g eas-cli eas login eas build:configure ``` ```bash # Bare React Native (when full native control is required) npx @react-native-community/cli init MyApp --template react-native-template-typescript cd MyApp npx pod-install ios # Install CocoaPods dependencies ``` ```bash # Run npx expo start # Expo dev server npx react-native run-ios # Bare RN iOS npx react-native run-android # Bare RN Android # Detox E2E setup npm install --save-dev detox @types/detox npx detox init ``` ## Fastlane CI/CD Example ```ruby # fastlane/Fastfile default_platform(:ios) platform :ios do lane :beta do increment_build_number( build_number: ENV["BUILD_NUMBER"] ) match(type: "appstore") build_app(scheme: "MyApp", configuration: "Release") upload_to_testflight(skip_waiting_for_build_processing: true) end lane :deploy do match(type: "appstore") build_app(scheme: "MyApp", configuration: "Release") upload_to_app_store(force: true, skip_screenshots: true) end end platform :android do lane :beta do gradle( task: "bundle", build_type: "Release", project_dir: "android/" ) upload_to_play_store(track: "internal") end lane :deploy do gradle(task: "bundle", build_type: "Release", project_dir: "android/") upload_to_play_store(track: "production", rollout: "0.1") end end ``` ## EAS Update (OTA) Example ```bash # Publish an update to the preview channel eas update --channel preview --message "Fix checkout crash" # Promote preview to production eas update --channel production --message "Stable release" ``` ```json // eas.json { "build": { "preview": { "distribution": "internal", "ios": { "simulator": false } }, "production": { "ios": { "buildConfiguration": "Release" }, "android": { "buildType": "apk" } } }, "update": { "channel": "production" } } ``` ## Documentation Sources Before generating code, consult these sources for current syntax and APIs: | Source | Tool | Purpose | |--------|------|---------| | React Native | `Context7` MCP | RN APIs, hooks, native modules, New Architecture APIs | | Expo | `Context7` MCP | EAS, SDK APIs, config plugins, expo-router | | Swift/SwiftUI | `Context7` MCP | SwiftUI views, Combine, platform integrations | | Kotlin/Compose | `Context7` MCP | Jetpack Compose, coroutines, platform integrations | | Fastlane | WebFetch docs.fastlane.tools | Lane actions, match, gym, pilot, deliver | | Detox | `Context7` MCP | E2E matchers, device API, configuration | ## Hard Prohibitions - Never use this skill for Flutter UI work — use `flutter-mobile` - No `AsyncStorage` for sensitive data — use `react-native-keychain` or `expo-secure-store` - No array index as `key` in FlatList/FlashList — use stable unique IDs - No inline functions in `renderItem` — use `useCallback` to prevent re-renders - No JS-thread animations — always use `useNativeDriver: true` or Reanimated 3 - No `console.log` in production — use a structured logger (e.g., `react-native-logs`) - No raw HTTP without SSL pinning for auth or payment endpoints - No secrets in JS bundle — use EAS secrets or native keystore ## Post-Code Review After writing code, dispatch these reviewer agents: - `code-reviewer` — general quality, DRY, error handling - `security-reviewer` — OWASP MASVS compliance, secure storage, network security - `flutter-security-expert` — only if the feature also has a Flutter counterpart that shares native code