Thread

A simple Isolated Thread wrapped with a type-safe Event Emitter for easier asynchronous communication.

Setup events for the thread to reply, or compute tasks individually.

Features

• Simple thread setup, control and communication
• Type-safe communication between threads
• Setup thread callbacks, using thread events
• Compute tasks individually

Getting started

Install it using pub:

dart pub add thread

And import the package:

import 'package:thread/thread.dart';

Usage

Setup a thread along with the initial function that will be running with it.

final thread = Thread((events) {
    ...
});

// Create a thread with no initial function
final thread = Thread.empty();

The thread will start automatically but you can prevent it from starting by setting the start parameter to false.

Inside the initial function, use the given EventEmitter to communicate. To make the most out of it, make sure to read the documentation here.

final thread = Thread((events) {
    events.on('data', (String data) async {
        ...
        events.emit('result', '<Computed> $data');
    });
});

Listen for the result outside the thread, and emit data whenever you need to compute something. Always emit thread-safe data.

thread.on('result', (String data) => print(data));

thread.emit('data', 'Hello World');

// [Output]
// <Computed> Hello World

You can also compute tasks individually with no setup needed. Tasks like this can be asynchronous, the result will be returned as a future.

The computation function will be executed in the thread, make sure to not use any objects that are not thread-safe.

// Send a single task for the thread to execute
print(await thread.compute(() => '<Computed> Hello World'));

// Compute a task along some input data
print(await thread.computeWith('Hello World', (String data) {
    return '<Computed> $data';
}));

// [Output]
// <Computed> Hello World

Controlling a Thread

Threads start automatically when you create them, the emitted events will be handled by the thread after starting.

You can also start it manually, make sure to set the start parameter to false.

final thread = Thread((events) { ... }, start: false);

await thread.start();
 ...

Stop the thread by using thread.stop() or thread.emit('end', true).

Start another isolated thread with the same object by using thread.start(), but only if the thread is not already alive.

A Thread execution can also be paused and resumed, using thread.pause() and thread.resume().

Addtional Methods

A temporary thread can be started with Thread.Compute and Thread.ComputeWith to compute a single task and return the result.

final computed = await Thread.Compute(() => '<Computed> Hello World');
final compute2 = await Thread.ComputeWith('Test', (String data) =>  '<Computed> $data');

print(computed);
print(compute2);

// [Output]
// <Computed> Hello World
// <Computed> Test

Careful when starting threads too quickly, starting a thread can be performance intensive. These methods should only be used when necessary, as in one time situation. Often is better to keep a single thread constantly open and idle.

GitHub

The package code is available on Github: Dart - Thread

Example

import 'package:thread/thread.dart';

void main() async {
  final thread = Thread((events) {
    events.on('data', (String data) async {
      await Future.delayed(const Duration(seconds: 1));
      events.emit('result', '<Computed> $data');
    });
  });

  thread.on('result', (String data) => print(data));

  thread.emit('data', 'Hello world!');
  thread.emit('data', 'Wow!');

  print(await thread.compute(() => 'Hello world!'));
  print(await thread.computeWith(123, (int data) => 'Wow $data'));

  // [Output]
  // Hello world!
  // Wow 123

  // <Computed> Hello world!
  // <Computed> Wow!
}