State Management for Mobile

Prerequisites: completed Mobile Fundamentals, comfort with React hooks (useState, useEffect).

Version note: verified against current npm and library documentation as of July 2026: zustand is at major version 5 (5.0.x). This project uses @react-native-async-storage/async-storage for Zustand's persist middleware, which is the standard, well-supported storage adapter across both Expo Go and development builds — react-native-mmkv is a faster alternative but requires a development build (it isn't supported in Expo Go), so it's called out as an upgrade path rather than the default. @tanstack/react-query is used for server-state (fetched data), which is the current mainstream pattern for separating client and server state in React Native apps.

Most "which state library should I use" debates dissolve once you separate two categories that get lumped together: client state (a theme toggle, a form draft, whether a modal is open — state your app owns) and server state (a list of posts fetched from an API — state a server owns, that you're caching a copy of). Client state changes instantly and locally; server state can be stale, needs refetching, and benefits from caching and retry logic you don't want to hand-write. This project uses Zustand for the former and TanStack Query for the latter, then persists only the client state that should survive an app restart.