TinyBase Persister for Expo FileSystem

A TinyBase persister that uses Expo FileSystem for persistent storage in React Native Expo apps.

Features

• Persists TinyBase stores to the device filesystem using Expo FileSystem API (v54)
• Auto-save and auto-load capabilities for seamless data synchronization
• Full TypeScript support with complete type definitions
• Compatible with both Store and MergeableStore
• Built on TinyBase v6+ with zero additional runtime dependencies
• Automatic file change polling for multi-instance synchronization

What is Persistence?

TinyBase Stores exist only in memory by default. Persisters solve this by enabling you to save and load your Store data to various storage backends. This is essential for:

• Maintaining application state across app restarts and device reboots
• Preserving user data between sessions
• Creating offline-first mobile applications
• Synchronizing data with external storage

Learn more about TinyBase persistence.

Usage

Assumes your Expo app already has Tinybase installed.

# npm
npm install @mote-software/tinybase-persister-expo-file-system

# pnpm
pnpm add @mote-software/tinybase-persister-expo-file-system

# yarn
yarn add @mote-software/tinybase-persister-expo-file-system

Peer Dependencies

This package requires:

• tinybase ^6.0.0
• expo-file-system ^19.0.17

Usage

import { createStore } from 'tinybase';
import { createExpoFileSystemPersister } from '@mote-software/tinybase-persister-expo-file-system';
import * as FileSystem from 'expo-file-system';

// Create a TinyBase store
const store = createStore();

// Define the file path (using Expo FileSystem v19+ API)
const filePath = `${new FileSystem.Directory(FileSystem.Paths.document).uri}/my-store.json`;

// Create the persister
const persister = createExpoFileSystemPersister(
  store,
  filePath,
  (error) => {
    console.error('Persister error:', error);
  }
);

// Load existing data and start auto-saving
await persister.startAutoLoad();
await persister.startAutoSave();

// Now your store is automatically persisted!
store.setCell('pets', 'fido', 'species', 'dog');
// This change is automatically saved to the file system

API Reference

createExpoFileSystemPersister

Creates a new persister instance that uses Expo FileSystem for storage.

function createExpoFileSystemPersister(
  store: Store | MergeableStore,
  filePath: string,
  onIgnoredError?: (error: any) => void
): ExpoFileSystemPersister

Parameters:

• store - The TinyBase Store or MergeableStore to persist
• filePath - Absolute path to the file (e.g., `${new FileSystem.Directory(FileSystem.Paths.document).uri}/store.json`)
• onIgnoredError - Optional callback for handling non-critical errors

Returns: An ExpoFileSystemPersister instance with all standard TinyBase Persister methods.

ExpoFileSystemPersister

Extends the standard TinyBase Persister interface with an additional method:

getFilePath()

Returns the file path used by this persister.

const filePath = persister.getFilePath();

Common Methods

All standard TinyBase Persister methods are available:

// Manual operations
await persister.save();    // Manually save store to file
await persister.load();    // Manually load store from file

// Automatic synchronization
await persister.startAutoSave();  // Auto-save on store changes
await persister.startAutoLoad();  // Auto-load on file changes
await persister.stopAutoSave();
await persister.stopAutoLoad();

// Status
const stats = persister.getStats();  // Get persistence statistics

File Change Detection

This persister uses a polling mechanism (checking every 1 second) to detect external file changes when startAutoLoad() is active. This enables synchronization between multiple app instances or external file modifications.

Example Project

Check out the complete example app in the apps/example directory of this repository for a working demonstration with a persistent counter.

Contributing

See CONTRIBUTORS.md for development setup, building, testing, and contribution guidelines.

Resources

• TinyBase Documentation
• TinyBase Persistence Guide
• Expo FileSystem Documentation (v54)
• GitHub Repository

License

MIT