Interview Questions
Platform.select() is a React Native utility that returns platform-specific values. It accepts an object with 'ios', 'android', and 'default' keys, returning the value that matches the current platform. It's commonly used for platform-specific styles, components, or behavior.
React Native automatically picks platform-specific files using extensions like .ios.js or .android.js. For example, Component.ios.js for iOS and Component.android.js for Android. This allows maintaining separate implementations while keeping a common interface.
Platform.OS is a string that identifies the current operating system ('ios' or 'android'). It's used for conditional rendering and logic based on the platform, allowing developers to handle platform-specific differences in code.
Platform-specific styles can be handled using Platform.select(), platform-specific style files, or conditional style objects. This includes handling different shadow implementations, native components styling, and platform-specific measurements.
React Native provides platform-specific components like DatePickerIOS and ProgressViewIOS for iOS, or DatePickerAndroid and ProgressBarAndroid for Android. These components are designed to match native platform UI guidelines and behavior.
Platform permissions are handled differently in iOS (Info.plist) and Android (AndroidManifest.xml). React Native provides APIs to request permissions at runtime, but setup and configuration must be done separately for each platform.
Android's back button is hardware/software-based and requires explicit handling using BackHandler, while iOS's back gesture is part of navigation and handled automatically by navigation libraries. Different approaches are needed for consistent behavior.
Font handling differs between platforms in naming conventions and loading mechanisms. iOS uses the font name, while Android uses the file name. Custom fonts require different setup in Xcode and Android assets folder.
Layout differences include status bar height, navigation bar presence, safe areas (iOS), and default spacing behaviors. These need to be handled using platform-specific components like SafeAreaView and appropriate styling.
Gestures can differ between platforms in behavior and implementation. iOS often uses swipe gestures for navigation, while Android relies more on the back button. PanResponder and gesture handlers need platform-specific configuration.
Native modules require separate implementations in Swift/Objective-C for iOS and Java/Kotlin for Android. This includes proper method mapping, event handling, and data type conversion while maintaining a consistent JavaScript interface.
iOS typically uses edge swipe gestures and navbar buttons, while Android uses the back button and different navigation patterns. Navigation libraries need platform-specific configuration for proper behavior and animations.
Animation implementations may need platform-specific tuning for timing, easing, and performance. Native drivers might work differently, and some animations may need platform-specific implementations for optimal performance.
Debugging tools and processes differ between platforms. iOS uses Xcode debugging tools while Android uses Android Studio. Chrome Developer Tools work differently, and native debugging requires platform-specific approaches.
Push notifications require different setup and handling for APNs (iOS) and FCM (Android). This includes different configuration, payload structures, and handling mechanisms while maintaining a consistent app experience.
App lifecycle events and background handling differ between iOS and Android. This includes different background modes, state restoration, and process lifecycle management requiring platform-specific implementations.
Storage mechanisms like AsyncStorage have platform-specific implementations and limitations. Secure storage, file system access, and data persistence require different approaches and configurations per platform.
Performance optimization requires platform-specific approaches for memory management, UI rendering, and native module optimization. Different profiling tools and optimization techniques are needed for each platform.
Network security configuration differs between platforms, including SSL pinning, network permissions, and security policies. Different configuration files and implementation approaches are needed for each platform.
Biometric authentication requires different implementations for Touch ID/Face ID (iOS) and Fingerprint/Face Unlock (Android). This includes different APIs, security models, and user experience considerations.
Complex features often require deep platform integration, custom native modules, and platform-specific optimizations. This includes handling different APIs, lifecycle management, and maintaining consistent behavior across platforms.
Hardware feature access requires platform-specific implementations for cameras, sensors, Bluetooth, and other hardware components. This includes different APIs, permissions, and optimization strategies.
UI automation requires different tools and approaches (XCTest for iOS, Espresso for Android). This includes different test writing strategies, CI/CD integration, and handling platform-specific UI elements.
App extensions (widgets, share extensions, etc.) require platform-specific implementation and configuration. This includes different development approaches, data sharing mechanisms, and lifecycle management.
AR features require platform-specific implementations using ARKit (iOS) and ARCore (Android). This includes different initialization, tracking, and rendering approaches while maintaining consistent AR experiences.
Payment integration requires platform-specific implementations for Apple Pay and Google Pay. This includes different APIs, security requirements, and user experience considerations while maintaining consistent payment flows.
Background processing requires different implementations for iOS background modes and Android services. This includes handling different lifecycle events, scheduling mechanisms, and power management considerations.
Accessibility implementation requires platform-specific considerations for VoiceOver (iOS) and TalkBack (Android). This includes different markup, focus management, and gesture handling while maintaining consistent accessibility.
Deep linking requires platform-specific configuration for Universal Links (iOS) and App Links (Android). This includes different setup processes, validation requirements, and handling mechanisms.
App signing and deployment differ significantly between iOS (certificates, provisioning profiles) and Android (keystore). This includes different build processes, signing mechanisms, and deployment procedures.