Concept of Isolates in Dart

Dart was traditionally designed to create single-page applications. And 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 own 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.

To use isolates you have to add import ‘dart:isolate’; statement in your program code.

Creating An Isolate In Dart

To create an isolate we make use of .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 In Dart

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

Syntax: isolate_name.kill( parameters );

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

Example:  Creating an isolate in Dart.

// importing dart libraries 

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

// Creating geek isolate 
Isolate geek; 

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(new 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.