Add and share a provider

Register it#

A provider is available to its own module as soon as it is listed:

@Module(controllers=[TaskController], providers=[TaskService])
class TaskModule:
    pass

Share it with another module#

Providers are private to their module by default. To let another module use one, export it:

@Module(
    controllers=[TaskController],
    providers=[TaskService],
    exports=[TaskService],
)
class TaskModule:
    pass

Then import the module that owns it:

@Module(imports=[TaskModule], controllers=[ReportController])
class ReportModule:
    pass

ReportController can now ask for TaskService. Importing a module gives you its exports, not its internals.

Provide a value or a factory#

For configuration, or anything not constructed by calling a class:

from bustan import Module, Provider

def make_client(settings: Settings) -> ApiClient:
    return ApiClient(base_url=settings.api_url, timeout=5.0)

@Module(
    providers=[
        Provider(token="SETTINGS", value=Settings()),
        Provider(provide=ApiClient, factory=make_client, inject=[Settings]),
    ],
    exports=[ApiClient],
)
class ClientModule:
    pass

Inject by token#

When the dependency is not a class:

from bustan import Inject

@Injectable()
class ReportService:
    def __init__(self, settings = Inject("SETTINGS")) -> None:
        self.settings = settings

Common error#

BustanResolutionError: TaskService is not available to ReportController.
  ReportModule imports [TaskModule]
  TaskModule exports []
  hint: add TaskService to TaskModule's exports

This almost always means the provider was registered but not exported.