this object cannot be resolved directly

Hi!

I’m having a bit of a problem with DependencyError: 'this' dependencies could only be used to instantiate classes error.

It’s limiting me in in case of scopes, especially applying Decorator Pattern:

class UsersModuleCommands(Injector):
    create_user_handler =  this.LoggingCreateUserCommandHandler.handler.

    class LoggingCreateUserCommandHandler(Injector):
        handler = LoggingCommandHandlerDecorator
        decoree = this.Handler.handler
        logger = (this << 1).logger

        class Handler(Injector):
            handler = CreateUserHandler
            transaction = (this << 2).transaction
            user_repository = (this << 2).user_repository

# transaction and logger are provided from outer-scope

I solved that by creating a “proxy class” that is constructed by Injector and is wrapping the decorated handler, but that’s hacky.

A similar problem arose when I needed to create a scope due to argument names not being unique, something like:

class Deps(Injector):
    service = this.ScopedDeps.service
    class ScopedDeps(Injector):
        service = A
        arg = (this << 1).config["arg"]
# config provided from outer-scope

Am I doing something wrong? 😉

PS: Thanks for all your hard work!

[wasinski]

That’s very kind! Thank you. I will need to implement something like “dynamic dependency injection” - creating of EventHandlers that share the same “infrastructure” dependencies (like transaction), and I expect that to be a little bit of a challenge, but for now, I will try to solve it on my own - I have some ideas around either using Sticky Scopes, or resolving it by using some custom wrappers around Injector that would hold such scoped dependencies. Thanks again though!

[proofit404]

I had a glance to the crewmate project and it looks like your’s approach is to override Injectors class definitions I found it a bit overwhelming to be redefining so many Injectors (we had loads of fakes then).

Yes, you are correct, at that moment we kinda forced to use this expression to reference neighbor nested Injector.

I can’t say how this approach annoys me. I hope I would came with something better in the future. And it won’t be yet another service locator implementation 😄

If you have any ideas what alternative solution could be, please file an issue 🙏