isolates_helper 0.4.2+1

An easy way to create multiple long live isolates to compute multiple functions, support Worker on the Web and try-catch block

Isolates Helper

• An easy way to create multiple long live isolates to compute multiple functions.

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

• Support try-catch block.

Usage

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.
  isolates.stream.listen((result) {
    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), () {
    isolates.stop();
  });
}

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
isolates.stream.listen((result) {
  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();

Worker

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 Create a file named worker.dart:

  import 'package:isolates_helper/isolates_helper.dart';
  
  main() {
    IsolatesHelper.workerFunction({
       /* Mapping between your function as String and real `Function`.
        This function MUST NOT depends on any Flutter library. */
      'add': add,
    });
  }
  

• Step 2: Run dart compile js worker.dart -o worker.js -O4 to compile Dart to JS (The flag -O4 is the obfuscated level of JS, the lowest value is -O0 and the highest value is -O4)

• Step 3: Copy worker.js to the Web folder (the same folder with index.html).

• Step 4: Now you can add worker to worker parameter like below:

  final isolates = IsolatesHelper(
    concurrent: 3,
    worker: 'worker',
    isDebug: true,
  );
  

• Step 5 Here is the way to execute a Worker function

  final result = await isolates(
    // Here is the normal function
    add, 
  
    // 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], 
    );
  

Contributions

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

Donations

If you like my work or the free stuff on this channel and want to say thanks, or encourage me to do more, you can buy me a coffee. Thank you so much!

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