WatermelonDB preloaded db

readme.md

This is the basic structure I'm using in an app.

getDatabasePath will handle any detail on unzip, copy, etc,

index will do all the usual dirty work, including withDatabase that won't explode if the database is missing

WatermelonProvider to cover original one til the DB is ready

getDatabasePath.android.js

import RNFS from "react-native-fs";

// Currently android will add `.db` to file name...
async function getDatabasePath(dbName) {
  let dbPath = `${RNFS.DocumentDirectoryPath}/${dbName}`;

  const exists = await RNFS.exists(dbPath.concat(".db"));
  if (!exists) {
    try {
      await RNFS.copyFileAssets(dbName.concat(".db"), dbPath.concat(".db"));
    } catch (e) {
      console.log(">>> getDatabasePath error", e);
    }
  }

  return dbPath;
}

export default getDatabasePath;

getDatabasePath.ios.js

import RNFS from 'react-native-fs';
import * as RNZIP from 'react-native-zip-archive

async function getDatabasePath(dbName) {
  let sanitizedDbName = dbName;

  if (!sanitizedDbName.endsWith(".db")) {
    sanitizedDbName = sanitizedDbName.concat(".db");
  }

  let dbPath = `${RNFS.DocumentDirectoryPath}/${sanitizedDbName}`;

  const exists = await RNFS.exists(dbPath);
  if (!exists) {
    const assetPath = `${RNFS.MainBundlePath}/${sanitizedDbName.replace(
      ".db",
      ".zip"
    )}`;
    const existsZip = await RNFS.exists(assetPath);
    if (existsZip) {
      const tmpPath = `${RNFS.DocumentDirectoryPath}/tmp`;
      await RNZIP.unzip(assetPath, tmpPath);
      await RNFS.moveFile(`${tmpPath}/${sanitizedDbName}`, dbPath);
      await RNFS.unlink(tmpPath);
    }
  }
  return dbPath;
}
export default getDatabasePath;

getDatabasePath.js

async function getDatabasePath(dbName) {
  let fullDbName = dbName;

  if (!fullDbName.endsWith('.db') && !fullDbName.includes('?')) {
    fullDbName = fullDbName.concat('.db');
  }

  let dbPath = dbName.includes(process.cwd())
    ? fullDbName
    : `${process.cwd()}/${fullDbName}`;

  return dbPath;
}

export default getDatabasePath;

index.ts

import getDatabasePath from './getDatabasePath';

const DEFAULT_DATABASE_NAME = 'watermelon';

const promises: { [key: string]: Promise<Database> } = {};
const instances: { [key: string]: Database } = {};

async function init(dbName: string = DEFAULT_DATABASE_NAME) {
  const dbPath = await getDatabasePath(dbName);

  const adapter = new SQLiteAdapter({
    schema,
    migrations,
    dbName: dbPath,
  });

  const instance = new Database({
    adapter,
    modelClasses,
    actionsEnabled: true,
  });
  instances[dbName] = instance;
  // sync();
  return db;
}


export const getDatabase = async (
  dbName: string = DEFAULT_DATABASE_NAME,
) => {
  if (!promises[dbName]) {
    promises[dbName] = init(dbName);
  }
  const instance = await promises[dbName];
  return instance;
};

// For _very_ specific uses
export const getDatabaseSync = (altDbName: string = DEFAULT_DATABASE_NAME) => {
  return instances[altDbName];
};

// custom withDatabase to handle the possibility of not having the database just yet...
export type Omit<T, K> = Pick<T, Exclude<keyof T, K>>;

export const withDatabase = <T extends DatabaseProp>(
  Wrapped: React.ComponentType<T>,
) => {
  const WrappedComponent: React.ComponentType<Omit<T, DatabaseProp>> = (
    props,
  ) => {
    const database = useDatabase();
    if (!database) {
      return <View />;
    }
    return <Wrapped {...(props as T)} database={database} />;
  };

  return WrappedComponent;
};

WatermelonProvider.js

import React, { ReactChild } from 'react';
import { Database } from '@nozbe/watermelondb';
import { getWatermelon } from 'app/utils/DBWatermelonOld/DBWatermelonOld';
import DatabaseProvider from '@nozbe/watermelondb/DatabaseProvider';

const WatermelonProvider = (props) => {
  const watermelonRef = React.useRef();
  const [database, setDatabase] = React.useState();

  if (!watermelonRef.current) {
    const promise = getWatermelon();
    if (promise) {
      watermelonRef.current = promise;
      watermelonRef.current.then(setDatabase);
    }
  }

  return database ? <DatabaseProvider database={database} {...props} /> : null;
};

export default WatermelonProvider;

I can say that this solution still work.
My personal struggle was that I misunderstood how I should create watermelon.db file, some sql statement packed into text file with .db extension not worked for some reason and I was able to solve it only by creating db file via "DB browser for sqlite".
I'm not sure if it will be difficult to prepopuate db later after multiple consecutive migrations.

Ok, @KosolapovR. I haven't had time to implement the solution yet, I had to prioritize other activities, but thanks for the feedback.

Thanks all! This is wonderful! I have a similar but a little different use case. Bottom line, I don’t want to use watermelondb for anything other than their Sync module. So I want to bring my SQLite database with my own schema etc created outside of watermelon and simply want to call the Sync module functions. Is this something I can do by following these instructions to add the extra columns to my tables so that watermelon then can handle the push / pull sync methods? Thanks!