Not only you have been isolated when pandemic from 2020 until 2022, Dart code also have experience with [isolated](https://api.flutter.dev/flutter/dart-isolate/Isolate-class.html) _(because by default dart run in the main isolates 🗿)_. ## Background Dart is single-threaded language. Dart programs run in the main isolate by default. It's the thread where a program starts to run and execute. So, all code inside `main()` will be run in main isolate. More detail, you can read a good explanation about that from [codemagic.io](https://blog.codemagic.io/understanding-flutter-isolates/) ## When I should use isolate As what I mention above, about dart is single-threaded language. But you can also make it multithreading if you have very heavy computation or process. All UI you see on your application is running in the `main thread` because all code on your Flutter App run inside main() function. ```dart void main() { runApp(MyApp()); } ``` You can create a new thread/isolate the process for heavy computation like render an image or do looping for 1 million times _(I'm not sure what are you doing with doing loop for 1 million times)_ or parse large JSON data to object like this: ![](https://raw.githubusercontent.com/lazycatlabs/blog.lazycatlabs.com-giscus/main/blog-assets/large_json.jpg) If you run that task in the `Main Thread`, you can block another process in the main thread, and maybe you can get this message on your application, and then make your application force close. ![](https://i.ytimg.com/vi/CxCO09U0okE/maxresdefault.jpg) ## Parse _(large)_ JSON data to the Object Parsing JSON data from API to the object is a very common task in the application. If you have small payload data, it's still safe to run the parsing code in the `main isolate`. But if you have large JSON data to load in `main isolate` that will make your App laggy (frame drop) while run the process. That's why we need to do that in the new isolate. You can see the example from [codewithandrea.com](https://codewithandrea.com/articles/parse-large-json-dart-isolates/). But from that example we need to do it for every response. ## Do it with Lazy way In this example, I will use some library. For the network, I'm using [Dio](https://pub.dev/packages/dio), and using [Freezed](https://pub.dev/packages/freezed) to create the models. #### Sample JSON response ```json { "meta": { "status": "200", "memoryusage": "2009952", "elapstime": 0.1006479263305664, "timestamp": 1683030115, "description": "Success" }, "data": [ { "id": "16124475-fbc6-4a3b-a4c9-xxXxxx", "name": "John Doe", "address": "Antartica", "status": 1 }, ... ] } ``` #### Create Isolate Parser ```dart import ... /// Pass T object, so we can use any kind of Object class class IsolateParser { final Map json; ResponseConverter converter; IsolateParser(this.json, this.converter); Future parseInBackground() async { final port = ReceivePort(); /// Create the isolate await Isolate.spawn(_parseListOfJson, port.sendPort); final result = await port.first; return result as T; } Future _parseListOfJson(SendPort sendPort) async { /// Parse Json to the object final result = converter(json); /// Use Isolate.exit for fast concurrency Isolate.exit(sendPort, result); } } ``` #### Create Dio Helper ```dart import ... /// Create typedef to convert Json Object typedef ResponseConverter = T Function(dynamic response); class DioClient { late Dio _dio; DioClient(){ _dio = _createDio(); } Dio get dio => _dio; /// Initialize Dio Dio _createDio() => Dio( BaseOptions( baseUrl: environment.baseUrl, headers: { 'Content-Type': 'application/json', 'Accept': 'application/json', }, receiveTimeout: const Duration(minutes: 1), connectTimeout: const Duration(minutes: 1), validateStatus: (int? status) { return status! <= 500 && status != 401; }, ), ); Future getRequest( String url,{ Map? queryParameters, required ResponseConverter converter, /// Create optional, incase you wan't to put /// it into new isolates bool isIsolate = true, }) async { try { final response = await dio.get(url, queryParameters: queryParameters); if ((response.statusCode ?? 0) < 200 || (response.statusCode ?? 0) > 201) { throw DioError( requestOptions: response.requestOptions, response: response, ); } if (!isIsolate) { /// Parse Json to the object in the main isolate return converter(response.data); } final isolateParse = IsolateParser( response.data as Map, converter, ); final result = await isolateParse.parseInBackground(); return result; } on DioError catch(e){ /// handle the error here } } } ``` #### Create Model class ```dart import ... part 'users_response.freezed.dart'; part 'users_response.g.dart'; @freezed class UsersResponse with _$UsersResponse { const factory UsersResponse({ Meta? meta, List? data, }) = _UsersResponse; factory UsersResponse.fromJson(Map json) => _$UsersResponseFromJson(json); } @freezed class User with _$User { const factory User({ String? id, String? name, String? address, int? status, }) = _User; factory Datum.fromJson(Map json) => _$DatumFromJson(json); } @freezed class Meta with _$Meta { const factory Meta({ String? status, String? memoryusage, double? elapstime, int? timestamp, String? description, }) = _Meta; factory Meta.fromJson(Map json) => _$MetaFromJson(json); } ``` #### Use isolate when fetch data from API ```dart ... final DioClient _clinet = DioClient(); Future fetchUser() async { /// So here, you just need to fetch data as usal /// We just do change in DioHelper with put IsolateParser /// inside method when calling getRequest final response = await _clinet.getRequest( "here the url to fetch user data", queryParameters: { "filter": "all" }, converter:(response) => UsersResponse.fromJson(response as Map

isolate

Isolates process in Dart