Navigating between scoped Screens

[troyjperales]

Cannot stress enough that Circuit wants you to use a good DI system + good data layer and just make presenters interpreters of that...

Related to this statement (from #1634), I have two typical Anvil scopes—a parent scope, AppScope and a child scope, LoggedInScope. The presenters that depend on LoggedInScope dependencies (and their corresponding UI) are scoped as such via factory code generation.

@CircuitInject(SignInScreen::class, AppScope::class)
class SignInPresenter @Inject constructor(...) : Presenter<SignInState> { ... }

@CircuitInject(HomeScreen::class, LoggedInScope::class)
class HomePresenter @Inject constructor(...) : Presenter<HomeState> { ... }

However, it's unclear how to navigate from an AppScope Screen (or the initial launched AppComponent-injected Activity) to a LoggedInScope Screen, since Circuit keys off the presenter/UI scopes that are given. When I try, I get the missing Screen error.

Is there an example of how to achieve this? Is this even considered "good DI"?

[troyjperales]

I just realized my Circuit instance is AppScope-ed. AFAIK the only way around this is to create a LoggedInScope-ed Circuit and launch a LoggedInScope-ed Activity.

[ZacSweers]

Yup correct. We expose Circuit.newBuilder() APIs to make this type of layering easier too

[ctbarbour]

I'm curious if there is a concrete example / code sample of how this actually works. I'm trying to figure out the best practice for navigating between scopes. Specifically, how to structure an AppScope and LoggedInScope which defines a UserSession instance which can then be injected to Presenter constructors.

I found this example from Amazon App Platform which isn't Circuit specific but I think demonstrates how to solve this problem with kotlin-inject-anvil. Not sure if this is the best solution in the context of Circuit though.