@rific/sync

A generic SQLite sync engine for Expo. Handles schema management, upsert/delete, and cursor-based sync state — so you can focus on fetching data, not wiring up tables.

Works with expo-sqlite's SQLiteDatabase out of the box.

Installation

npm install @rific/sync

Usage

import * as SQLite from 'expo-sqlite'
import { SyncEngine } from '@rific/sync'

const db = await SQLite.openDatabaseAsync('my.db')

const sync = new SyncEngine(db)

sync.register({
  name: 'products',
  schema: {
    id: 'TEXT',
    name: 'TEXT',
    price: 'REAL',
    stock: 'INTEGER',
  },
  primaryKey: 'id',
})

// Creates _sync_state and all registered tables (safe to call on every launch)
await sync.init()

Syncing records

// Fetch from your API, using the last cursor to get only new changes
const cursor = await sync.getCursor('products')
const { records, nextCursor } = await fetchProducts({ since: cursor })

for (const record of records) {
  if (record.deleted) {
    await sync.remove('products', record.id)
  } else {
    await sync.push('products', record)
  }
}

await sync.setCursor('products', nextCursor)

Transforming records

Use transform to reshape API responses before they hit SQLite:

sync.register({
  name: 'orders',
  schema: {
    id: 'TEXT',
    customer_id: 'TEXT',
    total: 'REAL',
    placed_at: 'TEXT',
  },
  transform: (record: ApiOrder) => ({
    id: record.id,
    customer_id: record.customerId,
    total: record.total,
    placed_at: record.placedAt,
  }),
})

API

new SyncEngine(db)

Creates a sync engine. db must satisfy the Database interface (automatically satisfied by expo-sqlite's SQLiteDatabase).

.register(config)

Registers a channel (table). Returns this for chaining.

| Field | Type | Description | |---|---|---| | name | string | Table name in SQLite | | schema | Record<string, ColumnType> | Column definitions | | primaryKey | string | Primary key column. Defaults to 'id' | | transform | (record: TRecord) => TRow \| Promise<TRow> | Optional transform before write |

.init()

Creates _sync_state and all registered tables if they don't exist. Safe to call on every app launch.

.push(name, record)

Upserts a record into the named channel's table.

.remove(name, id)

Deletes a record by primary key from the named channel's table.

.getCursor(name)

Returns the last saved cursor for a channel, or null if none exists.

.setCursor(name, cursor)

Saves a cursor for a channel along with a syncedAt timestamp.

License

MIT