Inject service with arguments

[mehmetgiritli]

I was wondering if it there is a way to inject a service which requires an argument to be provided in it's init?

I am aware of the parameters option in container config, and the possibility to pass those with Inject.

I am trying to pass an object from the code into a service basically, at injection time.

[maldoinc]

What you're describing should be doable via a factory. https://maldoinc.github.io/wireup/0.12.0/factory_functions/

You can request all dependencies you need in the factory and pass them down alongside your other thing you want to inject.

@service
def example_factory(container_deps_go_here) -> ExampleService:
    return ExampleService(container_deps, your_other_dependency)

Additionally if the object you're describing is also a service that was created somewhere else you can register that as a service directly and have it be injected as usual.

@service
def object_factory() -> OtherDependency:
   return fetch_object_from_somewhere

@service
class ExampleService:
    def __init__(self, other: OtherDependency) -> None:
        ...

Let me know if this helped otherwise feel free to add a bit more specific info.

[mehmetgiritli]

Thank you for your help with the examples. Here is what I'm trying to achieve:

Using FastAPI, I'm trying to inject a service and pass the Request object from FastAPI into it.

I think the Request aspect of it makes things a little more complicated, because it is not a dependency managed by wireup.

Here is an example of my failed attempt, while trying factory solution.

Inject the top level Keycloak service at the endpoint:

@app.get("/login")
def getLogin(keycloak: Annotated[Keycloak, Inject()]):
    return keycloak.login()

Keycloak service depends on Session service:

@service(lifetime=ServiceLifetime.TRANSIENT)
class Keycloak:
    def __init__(self, session: Session):

And Session service needs Request:

from fastapi import Request
...

@service(lifetime=ServiceLifetime.TRANSIENT)
class Session:
    def __init__(self, request: Request):

...

@service
def session_factory(request: Request) -> Session:
    return Session(request)

Of course it can't find the Request to inject.

Request is only available like this:

@app.get("/login")
def getLogin(request: Request, keycloak: Annotated[Keycloak, Inject()]):
    return keycloak.login()

But then I can not pass it to Keycloak's constructor.

[mehmetgiritli]

Probably need to wait for maldoinc/wireup#25 ?

[maldoinc]

I'm guessing you need your session to access request data? In any case I set up a quick PR that adds Request as a wireup dependency when using it with the fastapi integration.

Do check it out and let me know if you encounter any issues.

maldoinc/wireup#38

You can install it with the following command pip install git+https://github.com/maldoinc/wireup.git@fastapi-request-service. If it works as expected, I'll merge it because I do think it makes sense to have it even though I think it should be used sparingly.

Also, if you also find the Annotated[Keycloak, Inject()] syntax a bit ugly (which is sadly required in fastapi), you can create an alias to improve it somewhat.

T = TypeVar("T")
Autowired = Annotated[T, Inject()]

then you can use as Autowired[Keycloak] instead.

[iverberk]

Well, what a coincidence. I needed the request object in my authentication service (to grab the JWT token) and this seems to work just fine. Looking forward to this being merged!

[mehmetgiritli]

@maldoinc Many thanks for this, I can confirm the functionality works as expected. Much appreciated.

[maldoinc]

Thanks for the feedback! This is now released on 0.13.0.