Advanced concepts in Mobile Dev, page 6
Cross-Platform WebSockets with `web_socket_channel`
The web_socket_channel package abstracts away platform differences for WebSockets, giving you a single API for web, mobile, and server. Use it for real-time features like chat or live data feeds. The footgun: always await channel.ready before sending data.
ARKit: Building Augmented Reality on Apple Devices
ARKit is Apple's framework for blending digital objects with the real world using a device's camera. Use it for games, virtual furniture previews, or measurement tools.
Inline Requires: Defer JS Loading in React Native
Inline requires are just-in-time loading for code. Instead of loading everything at startup, you pull in modules only when needed, improving initial app speed. This is ideal for heavy components. The footgun: module side effects will execute later.
Core Bluetooth: The Central vs. Peripheral Model
Core Bluetooth lets your app talk to BLE devices by acting as a "Central" (scanner) or "Peripheral" (advertiser). Use it to read from sensors or make your app discoverable.
Testing with Hilt: Swapping Dependencies for Isolation
Hilt testing swaps real app components for fakes, isolating your code under test without manual setup. It's used in UI and unit tests to replace production dependencies like network clients with test doubles.
Profiling React Native on Android with System Tracing
System Tracing helps you find UI jank on Android by showing where time is spent in each 16ms frame. Use it in Android Studio to diagnose stuttering animations by inspecting the UI, JS, and Native Module threads.
AVCaptureSession
AVCaptureSession is the central coordinator in AVFoundation that connects camera and microphone inputs to outputs like a preview layer, photo capture, movie recording, or real time frame processing.
Drift: Type-Safe SQL in Dart & Flutter
Drift gives your raw SQL queries compile-time safety. Instead of parsing maps, its build-time analyzer validates your SQL and generates typed Dart objects for results. Use it to write complex queries without risking runtime errors from typos or schema changes.
Apple's Natural Language Framework
Apple's Natural Language Framework turns raw strings into structured meaning on-device without network calls. Tokenize queries or extract entities from user text locally. It is not infallible; heavy synchronous tagging on the main thread freezes your UI.
Isar: A Modern NoSQL Database for Flutter Apps
Isar is a fast, local NoSQL database for Flutter, offering static typing and ACID guarantees. Use it for on-device persistence in iOS, Android, and desktop apps. Don't mistake it for a remote database; Isar is for local storage, not cloud sync.
Turbo Modules: Type-Safe Native Code in React Native
Turbo Modules let your JS code call native APIs synchronously, skipping the slow async bridge. Use them to access device features or high-performance native libraries.
Full-Text Search in Local Flutter Databases
SQLite FTS5 is an inverted index in your app: words map to row IDs, skipping brute-force scans. Use it when local tables exceed thousands of rows and LIKE lags. The footgun is that FTS virtual tables never auto-sync, so stale indexes return wrong rows.
JSI Host Objects: Exposing C++ to JavaScript
A JSI Host Object is a C++ object exposed directly to your JavaScript runtime, bypassing React Native's slow, serializing bridge. It's used in high-performance native modules like database adapters.
Expedited Work: High-Priority Background Tasks in Android
Expedited work is for important, short tasks that must run quickly. It gets higher priority than regular background work without requiring a persistent notification. Use it for sending messages or saving notes.
JobScheduler: Efficient, Deferrable Background Tasks
Think of JobScheduler as Android's smart alarm for tasks. You specify conditions like 'Wi-Fi only' or 'charging,' and the OS runs your job efficiently to save battery. Use it for deferrable work like data syncs. Footgun: It's not for exact timing.
Handler and Looper: Android's Threading Backbone
A Looper is a worker that endlessly processes a queue of tasks for a thread. A Handler is how you give that worker a new task from another thread, like updating the UI. The footgun is blocking the main thread's Looper, which freezes your app.
measure: Baseline and Compare Code Performance
measure in XCTest establishes a performance baseline for a block of code and fails tests if it regresses. It tracks critical algorithm speed, running the code ten times for a stable average. The footgun is ignoring the baseline: you must set it first.
Detox: Gray-Box E2E Testing for React Native
Detox runs gray-box E2E tests by automatically synchronizing with your React Native app's activity. This eliminates flaky sleep() calls. Write one JavaScript test suite for iOS and Android that runs reliably on CI and real devices.
XCUITest Page Object Model: Tame Your UI Tests
The Page Object Model treats each app screen as an object, separating test logic from UI interaction. In XCUITest, this creates stable tests for complex apps. The biggest footgun is forgetting synchronization—always wait for views to load before interacting.
Snapshot Testing: Catch Unintended UI Changes
Snapshot testing compares your UI to a saved 'golden' image, failing if pixels differ. It's a visual diff for your views, catching unintended regressions in layout or style. The main footgun is forgetting to re-record snapshots after intentional UI changes.
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