Dependency Injection

Since Flutter does not support reflection (dart:mirrors), the project uses injectable as our dependency injection and service locator.

Injectable/GetIt

get_it is used as the IoC container of the project.

injectable is used with get_it to generate code for your dependency registrations.

Registration

Registration is called before running the application, as show here in our main.dart:

void main() {
  ...
  ServiceLocator.registerDependencies();
  ...
}

The class MyServiceImpl is annotated with @LazySingleton, meaning this class will only be initialized (once and only when needed) when resolving MyService.

import 'package:injectable/injectable.dart';

abstract class MyService{}

@LazySingleton(as: MyService)
class MyServiceImpl implements MyService {}

💡 TIP

• Use the snippet shortcut dep to create an abstract and concrete classes similar above.

Resolving

Given that you registered AppLogger:

import 'package:injectable/injectable.dart';

abstract class AppLogger{
  void log(String message);
}

@LazySingleton(as: AppLogger)
class AppLoggerImpl implements AppLogger {
  @override
  void log(String message) => /* do logging */;
}

You can resolve a dependency using the ServiceLocator.instance:

Future<void> main() async {
  // register first
  ServiceLocator.registerDependencies();

  // resolve
  final appLogger = ServiceLocator.instance<AppLogger>();
  appLogger.log('Hello World');
}