Everything in Mobile Dev, page 41
PixelRatio: Bridge Layout Units to Physical Pixels
PixelRatio is your app's translator, converting abstract layout units into physical pixels and respecting the user's chosen font size. Use it to fetch correct image sizes and make fonts accessible. Ignoring getFontScale() creates a fixed, inaccessible UI.
PermissionsAndroid: Requesting Runtime Permissions
PermissionsAndroid lets you ask for sensitive permissions like camera or location at runtime. Use its request method to show the native Android dialog. The biggest footgun is ignoring the NEVER_ASK_AGAIN result, which requires sending the user to system…
React Native: Navigating Platform-Specific Shadow Styles
React Native shadow APIs expose underlying platform differences. Use the web-like boxShadow for cross-platform consistency or the shadow* props for direct native control.
ActionSheetIOS: Native iOS Action Menus
ActionSheetIOS presents a native iOS menu sliding up from the bottom, offering users contextual choices. It's ideal for simple actions like "Delete" or "Save" and can also trigger the native share sheet.
SafeAreaView: Avoid Notches and Status Bars (Deprecated)
SafeAreaView was a component that automatically padded your UI to avoid device notches and system bars. It was a simple way to keep content visible on iOS, but it is now deprecated. The modern approach is to use the react-native-safe-area-context library.
WebSockets: A Persistent, Two-Way Connection
Think of a WebSocket as a dedicated phone line to a server, keeping the connection open for two-way conversation. It's ideal for real-time features like live chat or streaming stock tickers.
GraphQL Mutations: Writing Data to Your Graph
Think of a GraphQL mutation as a remote function call for writing data. Unlike REST, you declare what data you want back from the server in the same operation. Use it for creating, updating, or deleting data, like submitting a form or liking a post.
GraphQL: Ask for Exactly What You Need
GraphQL lets clients request exactly the data they need from a single endpoint, avoiding over-fetching. It's ideal for mobile apps, but beware of the N+1 problem where one query can trigger many database lookups on the backend.
AbortController: Stop Fetch Requests You No Longer Need
An AbortController is a kill switch for network requests. Use it to cancel a fetch when a user navigates away. The main footgun is not handling the AbortError that fetch throws, which can look like a real network failure.
FormData: The Right Way to Upload Files
FormData is your digital envelope for file uploads. It packages files and text into a multipart/form-data payload for fetch. Use it in React Native to upload images or videos. The footgun: don't set the Content-Type header yourself; fetch handles it.
Axios Interceptors: Middleware for Your API Calls
Axios Interceptors are like middleware for your API calls, letting you globally modify requests before they're sent or responses before they're handled. Use them to inject auth tokens or log activity. The footgun: request interceptors run last-in-first-out.
TanStack Query: Manage Server State, Not Client State
TanStack Query treats server data as a cache, not local state. It automates fetching, caching, and background updates to keep your React Native app in sync with your backend.
Axios: A Simpler Way to Make HTTP Requests
Axios simplifies making network requests by wrapping native browser APIs in a promise-based client. Use it to GET or POST data in any JavaScript app. The main footgun is forgetting requests are asynchronous; you must use async/await to get the data.
React Native: Making Network Requests with Fetch
fetch is your app's tool for requesting server data. It's asynchronous, returning a promise for a future response. Use it for API calls like loading profiles or posting updates. The footgun: always catch errors, or they will fail silently.
Immer: Write Mutable Code for Immutable State
Immer lets you write simple, mutable-style code to produce an immutable next state. It's essential in Redux or with React's useState to avoid complex spread operators for deep updates. The footgun: mutations are only safe inside Immer's produce function.
Memoized Selectors: Avoid Needless Re-renders
A memoized selector caches its result, re-running only if its inputs from the Redux store change. Use it to compute derived data like a filtered list without triggering needless re-renders.
Redux Saga: Managing Side Effects with Generators
Redux Saga runs side effects in a separate thread-like process. It listens for Redux actions and executes complex async tasks, like API calls, keeping that logic out of your components.
Redux Middleware: Intercepting Actions Before Reducers
Redux middleware is like an Express middleware for your state, intercepting actions before they hit the reducer. It's used for logging, crash reporting, or async API calls. The footgun is forgetting to call next(action), which silently blocks the action.
Jotai for React Native: Atomic State, Native Performance
Jotai brings minimalist, atomic state management to React Native, treating state as small, independent pieces. It's ideal for sharing state without prop drilling and offers full compatibility out of the box, including persistence via atomWithStorage.
Redux Toolkit: The Opinionated Way to Write Redux
Redux Toolkit (RTK) is the official, opinionated way to write Redux, bundling best practices to eliminate boilerplate. Use it for any new Redux app to simplify store setup and state updates.
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