Persistenza dello stato Zustand con AsyncStorage
Avvolga uno store Zustand nel middleware persist basato su AsyncStorage, così che lo stato sopravviva al riavvio dell’app, e gestisca i tempi della reidratazione.
Persistenza dello stato Zustand con AsyncStorage è una lezione React Native Academy gratuita su CoddyKit. Questa è la lezione 3 di 4. Puoi leggere la lezione completa qui gratuitamente — poi esercitati direttamente nel browser con un editor di codice integrato e un tutor IA disponibile 24/7. Fa parte del percorso di apprendimento React Native Academy, e i tuoi progressi si sincronizzano tra il web e l'app CoddyKit. Il corso React Native Academy include 4 lezioni in totale.
Parti di questa lezione non sono ancora state tradotte e vengono mostrate in inglese.
Why Persist State?
By default, Zustand state lives only in memory and is lost when the app closes. Persisting state means saving it to the device's local storage so it survives app restarts. This is essential for user preferences, authentication tokens, shopping carts, or any data the user expects to still be there when they reopen the app.
Installing AsyncStorage
AsyncStorage is the standard key-value storage API for React Native. In Expo managed workflow, install the community package @react-native-async-storage/async-storage. Zustand's built-in persist middleware works with any storage adapter, and AsyncStorage is the most common choice for mobile apps.
npx expo install @react-native-async-storage/async-storageAdding the persist Middleware
Wrap the store creator with persist imported from zustand/middleware. Pass it your store factory and a configuration object with a name key (the AsyncStorage key where state will be saved) and a storage key (pointing to your AsyncStorage adapter). Zustand handles reading and writing automatically.
import { create } from 'zustand';
import { persist, createJSONStorage } from 'zustand/middleware';
import AsyncStorage from '@react-native-async-storage/async-storage';
export const useSettingsStore = create(
persist<SettingsStore>(
(set) => ({
theme: 'light',
notifications: true,
setTheme: (theme) => set({ theme }),
toggleNotifications: () =>
set((state) => ({ notifications: !state.notifications })),
}),
{
name: 'settings-store',
storage: createJSONStorage(() => AsyncStorage),
}
)
);How Persist Works Internally
When the store is first created, persist reads from AsyncStorage and rehydrates (restores) any previously saved state before rendering the first component. When state changes via set, persist automatically serializes the state to JSON and writes it to AsyncStorage asynchronously. This all happens without any extra code in your components.
Handling the Rehydration Delay
AsyncStorage reads are asynchronous, so on the first render the store may still contain the initial state before rehydration finishes. Zustand's persist middleware adds a _hasHydrated flag and an onFinishHydration callback. Use these to show a loading screen while persisted state is loading from disk.
const hasHydrated = useSettingsStore((state) => state._hasHydrated);
if (!hasHydrated) {
return <ActivityIndicator />; // Show loading until store is ready
}
// Alternatively, listen to hydration completion:
useEffect(() => {
const unsub = useSettingsStore.persist.onFinishHydration(() => {
setReady(true);
});
return unsub;
}, []);Persisting Only Part of the State
You often do not want to persist everything in the store — for example, transient loading states or error messages should not be saved. Use the partialize option to select which fields to persist. The returned object contains only the keys you want to write to AsyncStorage.
persist<AuthStore>(
(set) => ({
user: null,
token: null,
isLoading: false, // transient — don't persist
error: null, // transient — don't persist
login: (user, token) => set({ user, token }),
logout: () => set({ user: null, token: null }),
}),
{
name: 'auth-store',
storage: createJSONStorage(() => AsyncStorage),
partialize: (state) => ({ user: state.user, token: state.token }),
}
)Versioning and Migration
When you change the structure of your persisted state in a new app release, old data on users' devices may not match the new shape. Use the version and migrate options to upgrade stored state from one version to the next. Increment version with each structural change and handle old state in the migrate function.
persist<SettingsStore>(
(set) => ({ /* ... */ }),
{
name: 'settings-store',
storage: createJSONStorage(() => AsyncStorage),
version: 2,
migrate: (persistedState: any, version: number) => {
if (version === 1) {
// Rename darkMode to theme in version 2
persistedState.theme = persistedState.darkMode ? 'dark' : 'light';
delete persistedState.darkMode;
}
return persistedState;
},
}
)Clearing Persisted State
To clear the persisted state — for example when the user logs out — call useStore.persist.clearStorage(). This removes the data from AsyncStorage. You can also call useStore.getState().reset() to clear the in-memory state at the same time. Doing both ensures the user starts fresh on the next app launch.
async function handleLogout() {
// Clear in-memory state
useAuthStore.getState().logout();
// Clear persisted state from AsyncStorage
await useAuthStore.persist.clearStorage();
navigation.reset({ index: 0, routes: [{ name: 'Login' }] });
}Using SecureStore for Sensitive Data
For sensitive values like auth tokens, prefer Expo SecureStore over plain AsyncStorage. SecureStore uses the device's secure enclave (iOS Keychain / Android Keystore) to encrypt data at rest. You can create a custom Zustand storage adapter using SecureStore's getItemAsync and setItemAsync methods.
import * as SecureStore from 'expo-secure-store';
const secureStorage = {
getItem: async (name: string) => await SecureStore.getItemAsync(name),
setItem: async (name: string, value: string) =>
await SecureStore.setItemAsync(name, value),
removeItem: async (name: string) =>
await SecureStore.deleteItemAsync(name),
};
// Use secureStorage instead of AsyncStorage:
storage: createJSONStorage(() => secureStorage),Debugging Persisted State
To inspect what is stored in AsyncStorage during development, call AsyncStorage.getAllKeys() and AsyncStorage.multiGet(keys) in the dev console or a debug screen. You can also manually clear stale persisted state with AsyncStorage.clear() when testing migration logic. Always test with a fresh install to simulate real user upgrade scenarios.
// Debug helper — call from a dev-only screen
async function printStorage() {
const keys = await AsyncStorage.getAllKeys();
const pairs = await AsyncStorage.multiGet(keys);
pairs.forEach(([key, value]) => {
console.log(key, ':', JSON.parse(value ?? 'null'));
});
}Persisting a Cart Store Example
Here is a realistic cart store that persists its items list across app restarts. Loading and error state are excluded from persistence using partialize. The total is derived on the fly in the component rather than stored, so it is always consistent with the items array after rehydration.
export const useCartStore = create(
persist<CartStore>(
(set, get) => ({
items: [],
addItem: (item) => set((state) => ({ items: [...state.items, item] })),
removeItem: (id) =>
set((state) => ({ items: state.items.filter((i) => i.id !== id) })),
clearCart: () => set({ items: [] }),
}),
{
name: 'cart-store',
storage: createJSONStorage(() => AsyncStorage),
partialize: (state) => ({ items: state.items }),
}
)
);Quick Check
Test your understanding of React Native Mobile Development concepts from this lesson.
Lesson Recap
In this lesson you learned: the persist middleware wraps a Zustand store to save and restore state from AsyncStorage automatically, partialize controls which fields are persisted to avoid saving transient loading or error state, and version with migrate handles breaking state shape changes across app updates. Next up we explore the slices pattern and Devtools integration in Zustand.
Domande Frequenti
La lezione «Persistenza dello stato Zustand con AsyncStorage» è gratuita?
Sì — il testo completo di «Persistenza dello stato Zustand con AsyncStorage» è gratuito qui sul web. Per esercitarvi in modo interattivo (un editor di codice integrato e un tutor IA 24/7) e sbloccare il resto del corso React Native Academy, passa a CoddyKit PRO. Il corso React Native Academy include 4 lezioni in totale.
Cosa imparerò in «Persistenza dello stato Zustand con AsyncStorage»?
Avvolga uno store Zustand nel middleware persist basato su AsyncStorage, così che lo stato sopravviva al riavvio dell’app, e gestisca i tempi della reidratazione. Eserciti React Native Academy con codice pratico che esegui direttamente nel browser, e un tutor IA 24/7 risponde alle tue domande mentre lavori sulla lezione.
Ho bisogno di esperienza per iniziare React Native Academy?
Non è richiesta alcuna esperienza precedente. React Native Academy su CoddyKit è strutturato per principianti e studenti avanzati, quindi puoi iniziare da qui o dall'inizio e procedere al tuo ritmo. Questa è la lezione 3 di 4.
Quanto tempo richiede la lezione «Persistenza dello stato Zustand con AsyncStorage»?
La maggior parte delle lezioni CoddyKit richiede circa 5–10 minuti. Ogni lezione è breve e interattiva, quindi fai progressi costanti e riprendi esattamente da dove hai lasciato su web e app.
Posso scrivere ed eseguire codice in questa lezione React Native Academy?
Sì. Ogni lezione React Native Academy include un editor di codice integrato, quindi scrivi ed esegui codice reale direttamente nel tuo browser e ricevi feedback istantaneo dall'IA — nessuna configurazione locale necessaria.
Tutte le lezioni di questo corso
- Creazione di uno store Zustand
- Lettura e aggiornamento dello stato dello store nei componenti
- Persistenza dello stato Zustand con AsyncStorage
- Pattern delle slice e integrazione con DevTools