driftWorkerMain function

void driftWorkerMain(
  1. QueryExecutor openConnection()
)

A suitable entrypoint for a web worker aiming to make a drift database available to other browsing contexts.

This function will detect whether it is running in a shared or in a dedicated worker. In either case, the openConnection callback is invoked to start a DriftServer that will serve drift database requests to clients.

When running in a shared worker, this function listens to SharedWorkerGlobalScope.onConnect events and establishes message channels with connecting clients to share a database. In a dedicated worker, a DedicatedWorkerGlobalScope.postMessage-construction is used to establish a communication channel with clients. To connect to this worker, the connectToDriftWorker function can be used.

As an example, a worker file could live in web/database_worker.dart and have the following content:

import 'dart:html';

import 'package:drift/drift.dart';
import 'package:drift/web.dart';
import 'package:drift/web/worker.dart';

void main() {
  // Load sql.js library in the worker
  WorkerGlobalScope.instance.importScripts('sql-wasm.js');

  driftWorkerMain(() {
    return WebDatabase.withStorage(DriftWebStorage.indexedDb('worker',
        migrateFromLocalStorage: false, inWebWorker: true));
  });
}

Depending on the build system you use, you can then compile this Dart web worker with dart compile js, build_web_compilers or other tools.

The connectToDriftWorker method can be used in the main portion of your app to connect to a worker using driftWorkerMain.

The documentation contains additional information and an example on how to use workers with Dart and Drift.

Implementation

void driftWorkerMain(QueryExecutor Function() openConnection) {
  final self = globalContext;
  _RunningDriftWorker worker;

  if (self is SharedWorkerGlobalScope) {
    worker = _RunningDriftWorker(true, openConnection);
  } else if (self is DedicatedWorkerGlobalScope) {
    worker = _RunningDriftWorker(false, openConnection);
  } else {
    throw StateError('This worker is neither a shared nor a dedicated worker');
  }

  worker.start();
}