Flutter: Asynchronous vs Isolates: Which One to Use When

Chapter 1: Understanding Basic Asynchronous Processing in Flutter

What is Asynchronous Processing?

Asynchronous processing is a method that enhances the efficiency of a program by executing multiple tasks concurrently. This way, it does not block the main synchronous code execution. This technique is particularly useful in programming languages like Dart used in Flutter where operations like I/O are inherently asynchronous.

Future and async-await in Flutter

In Flutter, asynchronous processing is implemented using the Future class and the async-await syntax.

• Future: This is a class in Dart that is used to represent a potential value or error that will be available at some point in the future. It is a core part of the Dart asynchronous programming ecosystem.
• async-await: These are keywords in Dart that help in writing asynchronous code that appears as if it were synchronous. An async function returns a Future, and the await keyword waits for this Future to complete and fetches the result.

How to use FutureBuilder

FutureBuilder is a widget in Flutter that simplifies the process of working with Futures. It provides a callback that triggers when the Future completes, allowing the UI to be updated with the result. Here is a simple example of its usage:

FutureBuilder(
  future: someAsynchronousFunction(),
  builder: (BuildContext context, AsyncSnapshot snapshot) {
    // Here you can construct the UI based on the snapshot.
  },
)

Chapter 2: Introduction to Isolates in Dart and Flutter

Basic concept of Isolate

In Dart, the concept of Isolate is introduced to handle concurrency. An Isolate can be considered as an independent worker that has its own memory heap and does not share any memory with other Isolates. This ensures that no two Isolates interfere with each other's state. You can read more about Isolates in the official Dart documentation.

Reason for using Isolates in Flutter

Since Flutter applications run on a single thread, performing CPU-intensive tasks on this thread can block the UI and lead to a poor user experience. By using Isolates, you can offload these tasks to a separate worker thread, thereby ensuring that the UI remains smooth and responsive.

Role of Isolates in Flutter

In Flutter, Isolates are used to handle CPU-intensive tasks such as image processing, file I/O, and database operations. By offloading these tasks to an Isolate, the main thread can focus on UI operations, leading to a smoother user experience.

Chapter 3: Differences between Asynchronous Processing and Isolates

Conceptual Differences between Asynchronous Processing and Isolates

Asynchronous processing and Isolates are two different ways of achieving concurrency in Dart and Flutter. While asynchronous processing allows tasks to run in parallel without blocking the main code execution, Isolates provide a way to perform more CPU-intensive tasks in separate threads.

Practical Differences between Asynchronous Processing and Isolates

Asynchronous processing is suitable for tasks that involve I/O operations, such as network requests or reading from and writing to a file. On the other hand, Isolates are more suited for CPU-intensive tasks that need to be run in parallel without affecting the performance of the main thread.

When to use Asynchronous Processing and when to use Isolates

• Asynchronous Processing: This is ideal for tasks that involve I/O operations, such as network requests, file operations, and accessing device APIs. Asynchronous processing ensures that these operations do not block the main thread and the user interface remains responsive.
• Isolate: An Isolate is suited for CPU-intensive tasks such as image processing, data processing, and encryption. By running these tasks in an Isolate, you can ensure that the main thread remains free to handle UI operations.

Chapter 4: Using Isolates in Flutter

Creating and Running Isolates

To create and run an Isolate in Flutter, you can use the spawn method of the Isolate class. Here is an example:

import 'dart:isolate';
void isolateFunction(SendPort sendPort) {
  // Write the code to run in the Isolate.
}
void main() async {
  // Create and run Isolate
  ReceivePort receivePort = ReceivePort();
  Isolate.spawn(isolateFunction, receivePort.sendPort);
}

Communication Between Isolates

Communication between Isolates in Dart is achieved using the SendPort and ReceivePort classes. Here is an example:

import 'dart:isolate';
void isolateFunction(SendPort sendPort) {
  // Write the code to run in the Isolate and send the result.
  int result = 42;
  sendPort.send(result);
}
void main() async {
  // Create and run Isolate
  ReceivePort receivePort = ReceivePort();
  Isolate.spawn(isolateFunction, receivePort.sendPort);
  // Receive the result in the main Isolate
  int result = await receivePort.first;
  print('Result: $result');
}

How to use the compute function

In Flutter, you can use the compute function to automatically spin up an Isolate, run a function on that Isolate, and return the result. Here is an example:

import 'package:flutter/foundation.dart';
int isolateFunction(int value) {
  // Write the code to run in the Isolate.
  return value * 2;
}
void main() async {
  int result = await compute(isolateFunction, 21);
  print('Result: $result');
}

Chapter 5: Practical Examples of Properly Utilizing Asynchronous Processing and Isolates

Example Using Asynchronous Processing

Here is an example of using asynchronous processing in Flutter to fetch JSON data from a server:

import 'dart:convert';
import 'package:http/http.dart' as http;
Future<Map<String, dynamic>> fetchData() async {
  final response = await http.get(Uri.parse('https://jsonplaceholder.typicode.com/todos/1'));
  if (response.statusCode == 200) {
    return json.decode(response.body);
  } else {
    throw Exception('Failed to load data');
  }
}
void main() async {
  Map<String, dynamic> data = await fetchData();
  print('Data: $data');
}

Example Using Isolates

Here is an example of using an Isolate in Flutter to perform a CPU-intensive task:

import 'dart:isolate';
import 'package:flutter/foundation.dart';
int countPrimes(int maxNumber) {
  int count = 0;
  for (int i = 2; i <= maxNumber; i++) {
    bool isPrime = true;
    for (int j = 2; j * j <= i; j++) {
      if (i % j == 0) {
        isPrime = false;
        break;
      }
    }
    if (isPrime) {
      count++;
    }
  }
  return count;
}
void main() async {
  int maxNumber = 1000000;
  int primeCount = await compute(countPrimes, maxNumber);
  print('Number of primes within $maxNumber: $primeCount');
}