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The shelf_modular uses modular_core to draw APIs! This means using the Modular framework in the backend as well, keeping the dependency injection system and routes work with REST and Websocket.

The Shelf#

The shelf is a middleware made for Dart inspired by the Connect of Javascript and also has some similarity to express.js.

The shelf_modular uses shelf to handle requests and responses, which makes it compatible with any other package made for shelf like shelf_proxy or *shelf_static *.

shelf_modular VS flutter_modular#

We have few differences between the two packages, the main one is that flutter_modular only works in a Flutter environment while shelf_modular depends on shelf, so the two packages are named with its main dependency in front: flutter_, shelf_.

In practice, shelf_modular is a clone of flutter_modular, returning a Response object in routes instead of a Widget.

A new constructor has been added to the dependency injection system called Bind.scoped, to keep the instance of a Bind during the request and destroy it at the end of the request. We will see how it works better later on.

Start a project#

To get started, we'll create a new Dart project using the dart create backend_app command or directly by the IDE you prefer.

ATTENTION

DO NOT CREATE A FLUTTER PROJECT!

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A version of Dart comes bundled with the Flutter SDK, so there is no need to download Dart separately.

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Maybe your new Dart project doesn't have the codes in the lib/ folder. This is default for Dart projects, but this might annoy Flutter developers, so we can create the lib/ folder and put your code there.

It is still recommended to start keeping the initialization file in the bin/ folder. So, we can just leave the file containing main() in the bin/ folder.

Now let's add shelf and shelf_modular directly into pubspec.yaml or using the command below:

dart pub add shelf shelf_modular

getting a result like this:


dependencies:  shelf: <last-version>  shelf_modular: <last-version>

We are now ready to start our API.

Starting the project#

We need to start Modular in our initialization file, that is, the one that contains the main() function. If you are following the pattern proposed in the tips above, this file will be in the bin/ folder.

bin/backend_app.dart

import 'package:shelf/shelf_io.dart' as io;import 'package:shelf_modular/shelf_modular.dart';
void main(List<String> arguments) async {    final server = await io.serve(Modular(module: AppModule()), '0.0.0.0', 3000);    print('Server started: ${server.address.address}:${server.port}');}

AppModule() is a class that inherits from Module, and which can be in the lib/ folder to make code more similar to a standard Flutter project for example.

lib/app_module.dart
import 'package:shelf/shelf.dart';import 'package:shelf_modular/shelf_modular.dart';
class AppModule extends Module {  @override  List<ModularRoute> get routes => [        Route.get('/', () => Response.ok('OK!')),      ];}

That is all! To start the project use the command:

dart run
// OR
dart bin/backend_app.dart
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The VSCode users can configure launch.json to have access to more debugging options like breakpoint.