Multiple Services

In this example, we’ll demonstrate how to use Dependy to manage multiple services within a module and retrieve them when needed. We'll create two simple services, LoggerService and MathService, register them in a DependyModule, and then access and use them in our main function.

import 'package:dependy/dependy.dart';

class LoggerService {
  void log(String message) {
    print('Log: $message');
  }
}

class MathService {
  int square(int number) => number * number;
}

// Define the Dependy module with LoggerService and MathService as providers
final dependy = DependyModule(
  providers: {
    DependyProvider<LoggerService>(
      (_) => LoggerService(),
    ),
    DependyProvider<MathService>(
      (_) => MathService(),
    ),
  },
);

void main() async {
  // Retrieve instances of LoggerService and MathService from the module
  final loggerService = await dependy<LoggerService>();
  final mathService = await dependy<MathService>();

  // Use the services
  loggerService.log('Calculating square of 4: ${mathService.square(4)}');
}

Explanation of the Code

1. Creating Services:

   • LoggerService: This service contains a log method, which prints a message to the console. It's designed for logging information.
   • MathService: This service provides a square method, which returns the square of a given integer. It serves as a simple mathematical utility.

2. Setting up the Dependy Module:

   • We define a DependyModule called dependy to organize and manage these services.
   • We add LoggerService and MathService as providers in the DependyModule using DependyProvider.
   • Each provider specifies how to create an instance of the respective service. Dependy will create each service only when it’s first requested, as it resolves providers lazily by default.

3. Retrieving and Using Services:

   • In the main function, we retrieve LoggerService and MathService by calling await dependy<LoggerService>() and await dependy<MathService>().
   • We then use LoggerService to log a message, which includes the result of mathService.square(4).

Key Points on Lazy Resolution

Dependy’s lazy resolution means that neither LoggerService nor MathService is created until we actually request them in the main function. This helps optimize resource usage by avoiding unnecessary service initialization.