Concept of Isolates in Dart

Dart was traditionally designed to create single-page applications. We also know that most computers, even mobile platforms, have multi-core CPUs. To take advantage of all those cores, developers traditionally use shared-memory threads running concurrently. However, shared-state concurrency is error-prone and can lead to complicated code. Instead of threads, all Dart code runs inside of isolates. Each isolate has its memory heap, ensuring that no isolate's state is accessible from any other isolate.

The isolates and threads are different than each other as in threads memory are shared whereas in isolates it is not. Moreover isolates talk to each other via passing messages.

Using Isolates in Dart

To use isolates, you have to add the below statement in your program code.

import 'dart:isolate';

Creating an Isolate

To create an isolate, we make use of the .spawn() method in Dart.

Syntax:

Isolate isolate_name = await Isolate.spawn( parameter );

This parameter represents the port that will receive the message back.

Destroying an Isolate

To destroy the isolate, we make use of the .kill() method in Dart.

Syntax:

isolate_name.kill( parameters );

We generally use spawn() and kill() together in a single program.

Example:

import 'dart:async';
import 'dart:io';
import 'dart:isolate';

// Creating geek isolate
Isolate? geek;

Future<void> start_geek_process() async {
    
    // port for isolate to receive messages.
    ReceivePort geekReceive = ReceivePort();
    
    // Starting an isolate
    geek = await Isolate.spawn(gfg, geekReceive.sendPort);
}

void gfg(SendPort sendPort) {
    int counter = 0;
    
    // Printing Output message after every 2 sec.
    Timer.periodic(const Duration(seconds: 2), (Timer t) {
        
        // Increasing the counter
        counter++;
        
        //Printing the output message
        stdout.writeln('Welcome to GeeksForGeeks $counter');
    });
}

void stop_geek_process() {
    
    // Checking the isolate with null
    if (geek != null) {
        stdout.writeln('--------------Stopping Geek Isolate--------------');
        
        // Killing the isolate
        geek!.kill(priority: Isolate.immediate);
        
        // Setting the isolate to null
        geek = null;
    }
}

// Main Function
void main() async {
    stdout.writeln('--------------Starting Geek Isolate--------------');
    
    // Starting the isolate with start_geek_process
    await start_geek_process();
    stdout.writeln('Press enter key to quit');
    
    // Whenever enter is hit the program is stopped
    await stdin.first;
    
    // Calling the stop_geek_process
    stop_geek_process();
    
    // Printing the goodbye message
    stdout.writeln('GoodBye Geek!');
    
    // Exiting the program.
    exit(0);
}

Output:

--------------Starting Geek Isolate--------------
Press enter key to quit
Welcome to GeeksForGeeks 1
Welcome to GeeksForGeeks 2
Welcome to GeeksForGeeks 3
Welcome to GeeksForGeeks 4
Welcome to GeeksForGeeks 5
Welcome to GeeksForGeeks 6
Welcome to GeeksForGeeks 7

--------------Stopping Geek Isolate--------------
GoodBye Geek!

Hitting enter after seventh output.