Isolates Helper


  • Creates multiple long-lived isolates to compute multiple functions.

  • Supports Worker and WASM on the Web with an efficient generator using the @isolatesHelperWorker annotation.

  • This package is based on the power of isolate_manager but can be used to compute multiple functions.

  • Support try-catch block.


Define the number of isolates you want to live with concurrent parameter.

void main() async {
  // Create 3 isolates to solve the problems
  final isolates = IsolatesHelper(concurrent: 3);

  // Listen for the results from the stream. {
    if (result is double) {
      print('Stream get addFuture: $result');
    } else {
      print('Stream get add: $result');

  // Compute the values. The return type and parameter type will respect the type
  // of the function.
  final added = await isolates.compute(addFuture, [1.1, 2.2]);
  print('add: 1.1 + 2.2 = $added');

  // Multiple computations at the same time are allowed. It will be queued
  // automatically.
  for (int i = 0; i < 10; i++) {
    isolates(add, [i, i]).then((value) async {
      print('add: $i + $i = $value');

  // Stop the IsolateHelper instance after 5 seconds
  Timer(Duration(seconds: 5), () {

Future<double> addFuture(List<double> values) async {
  return values[0] + values[1];

int add(List<int> values) {
  return values[0] + values[1];

Here is the ways to use try-catch block:

// Catch the error from the stream {
  print('Stream get add: $result');
}).onError((e) {
  print('Error from stream: $e');

// Catch the error from the try-catch block
try {
  await isolates.compute(addException, [1, 1]);
} catch (e) {
  print('Error from try-catch: $e');

The first compute will automatically wait for all isolates to started before doing the computation, if you want to wait for it manually, you can use:

await isolates.ensureStarted;

Or you can check if the current isolates are started or still in processing by using:

bool isStarted = isolates.isStarted;

You can restart all the isolates with:

await isolates.restart();

Remember to stop the isolates when you don't need it:

await isolates.stop();


You need to do a little bit more works then using normal Isolate but don't worry, the below steps will help you to do it easily.

  • Step 1: Add @isolatesHelperWorker annotation to the functions that you want to use for the Worker

    Future<double> addFuture(List<double> values) async {
      return values[0] + values[1];
    int add(List<int> values) {
      return values[0] + values[1];
  • Step 2: Run this command

    dart run isolates_helper:generate
  • Step 3: Add the worker to the IsolatesHelper

    final isolates = IsolatesHelper(
      concurrent: 3,
      worker: 'worker',
      isDebug: true,
  • Step 4: Here is the way to execute a Worker function

    final result = await isolates(
      // Here is the normal function
      // Here is the normal params
      [2, 3], 
      // Here is the name of the function that is mapped in the step 2
      workerFunction: 'add',
      // [Optional] the normal params will be used if this value is null
      workerParams: [2, 3], 


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


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