dart_thread 0.0.5

Mapping isolates and web workers to single interface, that allow to write one code for different platforms

Mapping isolates and web workers to single interface

Features

Provides one interface to writing isolates for desktop and web workers to web platform.

You need to create a new class extend DartThread and override methods:

1. onGetMessage - for receiving a messages from main thread
2. onExecute - for execution task in thread
3. messageToObject - for mapping custom class to web worker

Usage

class TestThread extends DartThread {

  // Need to mapping Class to super.init, 
  // because dart did not allow override a static method
  static TestThread newInstance() => TestThread(); 

  @override
  Future<void> onExecute(Function(dynamic message) sendMessage) async {

    while (true) {
      sendMessage(Random().nextInt(100));
      await Future.delayed(Duration(seconds: 1));
    }

  }

  @override
  Future<void> onGetMessage(message, Function(dynamic message) sendMessage) async {

    sendMessage(message);

  }

}

In app:

main() async {

  TestThread testThread = TestThread();

  await testThread.init(TestThread.newInstance, (message) {

    print(message);

  });

  testThread.sendMessage('echo');

  await Future.delayed(Duration(seconds: 10));

  testThread.deInit();

  exit(0);

}

Prepare web worker

1. Create web worker dart file with name of a class, for example TestThread.dart:

@JS()

import 'dart:html';
import 'dart:js_interop';
import 'dart_thread_example.dart';

@JS('self')
external DedicatedWorkerGlobalScope get self;

void main() async {

  await TestThread().main(self);

}

2. Compile dart file to js using command-line:

set "dart_path=D:\sdk\flutter\bin\cache\dart-sdk\bin"
set "flutter_web_sdk=D:\sdk\flutter\bin\cache\flutter_web_sdk"

call "%dart_path%\dart" compile js -O2 --libraries-spec="%flutter_web_sdk"\libraries.json -o web/TestThread.dart.js lib/TestThread.dart || pause

3. Move dart.js file in web folder of Flutter app

Send custom classes to web worker

class CustomClass {
  Map<String, dynamic> toJson() => {
    'runtimeType': 'CustomClass',
    // other properties
  };
}

class TestThread extends DartThread {
  @override
  dynamic messageToObject(dynamic message) {
    if (message is Map<String, dynamic>) {
      if (message['runtimeType'] == 'CustomClass') 
        return CustomClass.fromJson(message);
    }

    return super.messageToObject(message);
  }
}