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An easy way to create a new isolate, keep it active and comunicate with it. It supports sending and receiving values between main and child isolate multiple times via stream.

Isolate Contactor #

  • This package is different from the compute method, IsolateContactor allows the isolate to run, send, receive data until you terminate it. It'll save a lot of starting time.

  • This package will be moved to isolate_manager: pub | git in the future.

Features #

  • Easy to create a new isolate, keep it active and comunicate with it. You can use isolate_manager: pub | git to create multiple isolate for a function at the same time which using this plugin as its core.
  • Supports Web with Future and Worker (Worker is the real Isolate on Web). Automatically switch to Future if current Web browser doesn't support Worker.
  • Supports sending and receiving values between main and child isolate multiple times via stream, so you can build your widget with StreamBuilder and always listen to the new value from your isolate.

Basic Usage (with build-in function) #

There are multiple ways to use this package, the only thing to notice that the function have to be a static or top-level function to make it works.

Create a top-level or static function #

double add(dynamic value) => value[0] + value[1];

Create IsolateContactor instance for that function #

IsolateContactor<double> isolateContactor = await IsolateContactor.create(add);

Listen to the result of the isolate #

The result will be passed into stream listener, so you need to make sure that the stream has been called before sending message to the isolate for computing.

In Dart native:

isolateContactor.onMessage.listen((message) {
  print('Result of the `add` function: $message');

In Flutter:

  stream: isolateContactor.onMessage,
  builder: (context, snapshot) {
    if (!snapshot.hasData) {
      return const Center(
        child: CircularProgressIndicator(),
    return Text(
        'Result of the `add` function: ${}');

Send data to isolate for computing #

isolateContactor.sendMessage([10.0, 20.0]);

You can also await for the result #

final result = await isolateContactor.sendMessage([10.0, 20.0]);

Create your own isolate function #

This is also not too complicated to use, you're completely control your isolate function with this method. You just need to create a function of this form:

// Create your own function here
void isolateFunction(dynamic params) {
  // Initial the controller for child isolate
  final controller = IsolateContactorController<double>(
    onDispose: () {
      print('Dispose isolateFunction');

  // Get your initialParams.
  // Notice that this `initialParams` different from the `params` above.
  final initialParams = controller.initialParams;

  // Listen to the message receiving from main isolate
  controller.onIsolateMessage.listen((message) {
    // Do your stuff here
    final result = add(message[0], message[1]);
    // Send value back to your main process in stream [onMessage]

Then create IsolateContactor for that function #

IsolateContactor<double> isolateContactor =  await IsolateContactor.createOwnIsolate(
      initialParams: 'This is initialParams',
      debugMode: true,

Then you can use isolateContactor like above example #

Configuration for Worker (Real Isolate on Web) #

  • Step 1: Download isolate_contactor/worker/function_name.dart and rename it to the <function_name>.dart that you want to create isolate.

  • Step 2: Modify the function dynamic functionName(dynamic message) in the script to serves your purposes. Then rename it to the same as the above <function_name> (Just helping you easier to remember for later use). You can also use the top-level or static function that you have created above.

    You should copy that function to separated file or copy to <function_name>.dart file to prevent the dart compile js error because some other functions depend on flutter library.

  • Step 3: Run dart compile js <function_name>.dart -o <function_name>.js -O4 to compile dart to js (-O0 to -O4 is the obfuscated level).

  • Step 4: Copy <function_name>.js to web folder (the same folder with index.html).

  • Step 5: Now you can add parameter workerName to your code like below:

    IsolateContactor<double> isolateContactor = await IsolateContactor.create(
        workerName: 'add', // add.js

    Now the plugin will handle all other action to make the real isolate works on Web.

Additional #

  • If the function_name.dart show errors for js package, you can add js to dev_dependencies:

      js: ^0.6.4
  • IsolateContactor.create and createOwnIsolate include converter and workerConverter parameters which helping you to convert the result received from the Isolate (converter) and Worker (workerConverter) and send it to the result. Example:

    IsolateContactor<Map<int, double>> isolateContactor =
        await IsolateContactor.create(
      workerName: 'map_result',
      workerConverter: (result) {
        final Map<int, double> convert = {};
        // Convert Map<String, String> (received from Worker) to Map<int, double>
        (jsonDecode(result) as Map).forEach((key, value) => {
              convert.addAll({int.parse(key): double.parse(value)})
        return convert;

Contributions #

If you encounter any problems or feel the library is missing a feature, please feel free to open an issue. Pull request are also welcome.

To-do list #

  • Await for the result from isolate when using isolateContactor.sendMessage.
  • Allow creating multiple child isolates at the same time to solve multiple inputs sent from main isolate. Move this feature to isolate_manager: pub | git
  • Add real isolate for web platform with service-worker.js.
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verified publisher

An easy way to create a new isolate, keep it active and comunicate with it. It supports sending and receiving values between main and child isolate multiple times via stream.

Repository (GitHub)


API reference


Icon for licenses.MIT (LICENSE)




Packages that depend on isolate_contactor