Persistence Setup

To persist store fields across sessions, mobx-chunk lets you plug in any storage engine via configurePersistenceEngine. Below are examples for React Native (MMKV, AsyncStorage) and web (localStorage).

configurePersistenceEngine

Before using any persisted chunks, initialize the persistence engine once in your app’s entry point:

import { configurePersistenceEngine } from "mobx-chunk";

configurePersistenceEngine({
  clear: () => {/* remove all keys */},
  get:   (key: string) => /* return string | Promise<string | null> */,
  remove:(key: string) => /* remove one key */,
  set:   (key: string, value: string) => /* set one key */,
});

• clear(key?): Remove all or scoped entries.
• get(key): Return the stored string or a promise resolving to it.
• remove(key): Delete a specific key.
• set(key, value): Store a string value.

React Native: MMKV Example

import React from "react";
import { MMKV } from "react-native-mmkv";
import { configurePersistenceEngine } from "mobx-chunk";

const storage = new MMKV();

configurePersistenceEngine({
  clear: () => storage.clearAll(),
  get:    (key) => storage.getString(key),
  remove: (key) => storage.delete(key),
  set:    (key, value) => storage.set(key, value),
});

const App = () => (
  // Your app goes here
  <></>
);

export default App;

React Native: AsyncStorage Example

import React from "react";
import AsyncStorage from "@react-native-async-storage/async-storage";
import { configurePersistenceEngine } from "mobx-chunk";

configurePersistenceEngine({
  clear:  () => AsyncStorage.clear(),
  get:    (key) => AsyncStorage.getItem(key),
  remove: (key) => AsyncStorage.removeItem(key),
  set:    (key, value) => AsyncStorage.setItem(key, value),
});

const App = () => (
  // Your app goes here
  <></>
);

export default App;

React (Web): localStorage Example

import React from "react";
import { configurePersistenceEngine } from "mobx-chunk";

configurePersistenceEngine({
  clear:  () => Promise.resolve(localStorage.clear()),
  get:    (key) => Promise.resolve(localStorage.getItem(key)),
  remove: (key) => Promise.resolve(localStorage.removeItem(key)),
  set:    (key, value) => Promise.resolve(localStorage.setItem(key, value)),
});

const App = () => (
  // Your app goes here
  <></>
);

export default App;

Debounce Control

By default, persistence writes are debounced by 300 ms to avoid excessive storage operations. You can customize this per chunk with persistDebounce:

export const store = createChunk({
  name: "settings",
  initialState: { theme: "light" },
  persist: ["theme"],
  persistDebounce: 500, // write at most once every 500ms
});

Set persistDebounce: 0 for immediate writes, or increase the value for stores that update very frequently.

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With the engine configured, any chunk using the persist option will automatically read and write state to your chosen storage backend.