Is there any example project that combines backsta...

# compose

[Ricardo C.]

Is there any example project that combines backstack + keeping screen state + dependency injection via params? ie, a regular app we're used to. more than the simple examples

[jim]

Have you seen Jetnews (https://github.com/android/compose-samples/tree/master/JetNews) or are you looking for something even more complex than that?

[Zach Klippenstein (he/him) [MOD]]

This is probably overkill, but Square’s Workflow library is very DI friendly and (theoretically) integrates very well with Compose: https://github.com/square/workflow-kotlin-compose. Unfortunately there’s currently an issue with a bug in the IR backend that prevents compiling workflows and compose code in the same module, but you can use an older version of the library with Compose fine.

[Ricardo C.]

hm... last time I checked JetNews it didn't have DI or backstack. But seems like it's still missing a backstack and keeping state per backstack entry 🤔

[Ricardo C.]

Tbh I had checked workflow before but I don't find it very easy to get into. it has a bit of a steep learning curve 😕

[Ricardo C.]

I see that JetNews does injection via params but it's very manual. It only touches the graph at a very high level:

AppContent(
            navigationViewModel = navigationViewModel,
            interestsRepository = appContainer.interestsRepository,
            postsRepository = appContainer.postsRepository
        )

From this point below it's manual.

I've been trying to do all of these automatically with dagger but always hit some issue that I don't know how to get around

[Ricardo C.]

I've managed to inject everything automatically into "screen" classes that have a render composable but I can't figure how to access the navigator. and can't pass it through ambients because it's generic

[Ricardo C.]

was hoping to find some more mature example done by someone that knows more than me 😅

[Zach Klippenstein (he/him) [MOD]]

Can your screens take callbacks for navigation, instead of passing the navigator through directly?

[Ricardo C.]

I don't think so. I was trying to map destinations -> screens using multibinds. I was trying to avoid going into the big when route

[Ricardo C.]

Even with assisted inject, I would have to have a multibinds of factories. but the parameters for each factory could be different, so I would have to use the big when

[Adrian Blanco]

I've tried some small work with it, but it's also architecturally a really messy problem to get right :p

https://github.com/adrianblancode/Cheddar

[Fudge]

You can have “injection” with ambients

[Fudge]

A parent provides an ambient with a value and a very deep child can consume it

[popalay]

You can check out my home project: Square workflow + compose + Koin Di + backstack
https://github.com/Popalay/Tracktor-ComposeUI

[Joost Klitsie]

You can pass on a dependency object down the ambient line. I did a dependency injection with Kodein and Compose, here are the helper functions:

val DIAmbient = ambientOf { DI {} }

@Composable
inline fun <reified T : Any> instance(): DIProperty<T> = DIAmbient.current.instance()

@Composable
inline fun <reified A : Any, reified T : Any> instance(arg: A?): DIProperty<T> = arg?.let {
    DIAmbient.current.instance<A, T>(arg = it)
} ?: instance()

object EmptyProps

@Composable
fun composeSubDI(
    diBuilder: DI.MainBuilder.() -> Unit,
    props: Any = EmptyProps,
    content: @Composable() () -> Unit
) = Providers(
    DIAmbient provides remember(
        props,
        calculation = { subDI(DIAmbient.current, init = diBuilder) }),
    children = content
)

Usage is simple:

@Composable
fun loginComponent() {
    composeSubDI(diBuilder = {
        import(loginViewModule())
    }) {
        val viewModel by instance<LoginContract.ViewModel>()
        val viewState = viewModel.viewState.collectAsState(AndroidUiDispatcher.Main).value
        Column {
            OutlinedTextField(value = viewState.userName, onValueChange = viewModel::updateUserName, label = {})
            OutlinedTextField(value = viewState.password, onValueChange = viewModel::updatePassword, label = {})
            OutlinedButton(onClick = viewModel::onLoginPressed) { Text("Login") }
        }
    }
}

[Joost Klitsie]

basically this will create sub DI objects that are scoped to the compose scope they are in

[Joost Klitsie]

It is just important to make sure that for example the ViewModel binding is a singleton (within the scope) 🙂