MetroX ViewModel Compose¶

Compose integration for MetroX ViewModel. This artifact provides Compose-specific utilities for injecting ViewModels.

Should I use this?

Well, that’s up to you! This artifact is mostly for projects coming from heavy use of more vanilla Android architecture components or hiltViewModel() use. Modern Android apps should use higher level architectures like Circuit*, Voyager, etc. that abstract away ViewModel management.

*Disclosure: I am one of the authors of Circuit, and I’m a big fan of it!

Usage¶

dependencies {
  implementation("dev.zacsweers.metro:metrox-viewmodel-compose:x.y.z")
}

This artifact depends on metrox-viewmodel transitively.

Setup¶

1. Set up your graph¶

Create a graph interface that extends ViewModelGraph:

@DependencyGraph(AppScope::class)
interface AppGraph : ViewModelGraph

2. Provide LocalMetroViewModelFactory¶

At the root of your Compose hierarchy, provide the factory via CompositionLocalProvider:

@Composable
fun App(metroVmf: MetroViewModelFactory) {
  CompositionLocalProvider(LocalMetroViewModelFactory provides metroVmf) {
    // Your app content
  }
}

On Android, inject the factory into your Activity:

@Inject
class MainActivity(private val metroVmf: MetroViewModelFactory) : ComponentActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContent {
      CompositionLocalProvider(LocalMetroViewModelFactory provides metroVmf) {
        App()
      }
    }
  }
}

Using ViewModels¶

Standard ViewModels¶

Use metroViewModel() to retrieve injected ViewModels:

@Composable
fun HomeScreen(viewModel: HomeViewModel = metroViewModel()) {
  // ...
}

Assisted ViewModels¶

For ViewModels with ViewModelAssistedFactory:

@Composable
fun DetailsScreen(
  data: String,
  viewModel: DetailsViewModel = assistedMetroViewModel()
) {
  // ...
}

Manual Assisted ViewModels¶

For ViewModels with ManualViewModelAssistedFactory:

@Composable
fun CustomScreen(
  viewModel: CustomViewModel = assistedMetroViewModel<CustomViewModel, CustomViewModel.Factory> {
    create("param1", 42)
  }
) {
  // ...
}