DI - Exported singleton binds are not shared between modules

[tspoke]

Describe the bug

When I use exported bind in a module, if I import this module the instance is not shared BUT the instance is re-created by each module.

In the example below, the AuthService constructor is called 2 times instead of 1 and the instance is different.

Even if my app architecture may be discussed, I expect a singleton in a DI system to be a singleton not a factory.

To Reproduce

class AppModule extends Module {
  @override
  List<Module> get imports => [AuthModule()];  // <<--- I need to import it to use the exported AuthenticatedHttpClient

  @override
  List<Bind> get binds => [
    Bind.singleton<AppEndpoints>((i) => AppEndpoints(i<AuthenticatedHttpClient>().client), export: false),
  ];

  @override
  List<ModularRoute> get routes => [
    ModuleRoute(Routes.auth, module: AuthModule()),  // AuthModule expose Routes too..
  ];
}

class AuthModule extends Module {
  @override
  List<Bind> get binds => [
    Bind.singleton<AuthenticatedHttpClient>((i) => AuthenticatedHttpClient.build(i(), AuthInterceptor(i())), export: true),
    Bind.singleton<AuthService>((i) => AuthService(i(), i()), export: true),
    Bind.factory<AuthController>((i) => AuthController(i(), i())),
    Bind.factory<AuthScreen>((i) => AuthScreen()),
  ];

  @override
  List<ModularRoute> get routes => [ChildRoute("/", child: (context, args) => AuthScreen())];
}

Expected behavior
When exporting a singleton, I expect the instance to be shared between different modules even if I import it multiple times.

[AlvaroVasconcelos]

Hi, what version of flutter_modular is being used?
Check if this occurs in the current version (4.5.x)

[tspoke]

Hi @AlvaroVasconcelos

Thank you for your support.
I was on 4.4.0 and I updated to 4.5.0 and I have the exact same problem.

I don't have too much time these days to give a look into the framework to find the cause but I will if I found some free time.

[tspoke]

I created a small project here : https://github.com/tspoke/modular-module-binding-bug

Hereafter the console, you can see that the UserService is re-created each time the UserModule starts :

What you can see :

• The AppModule starts and instanciates the UserService (its an exported service)
• If I go to the UserScreen, I can see that the Modular.get() will use the SAME instance than the AppModule in UI, BUT the UserService is still instanciated by the Injector on init
• If I pop() back to AppScreen, the module is destroyed
• Going again in UserScreen will init a new userModule and create the UserService singleton again.

Note that the UserScreen always use the same UserService binding even if it is re-instanciated each time.

You can try my project, I tested different injection methods. Check the logs to see the problem :)

[tspoke]

Sorry for upping this issue @AlvaroVasconcelos but this is blocking :/ Do you have an idea on this problem ?

[jacobaraujo7]

Fixed!
Please, wait Modular v5.0.0

[tspoke]

Thank you very much @jacobaraujo7, do you have an ETA for this v5 ?

[jacobaraujo7]

Thank you very much @jacobaraujo7, do you have an ETA for this v5 ?

arriving this week