Hilt Usage Sample for Mavericks

This module contains a sample app demonstrating how to setup Hilt and AssistedInject in an app using Mavericks.

// build.gradle

dependencies {
    def hiltVersion = "2.31.0" // or newer.
    kapt "com.google.dagger:hilt-android-compiler:${hiltVersion}"
    implementation "com.google.dagger:hilt-android:${hiltVersion}"
}

Key Features

• Injecting state into ViewModels with AssistedInject

  Since the initialState parameter is only available at runtime, we use the AssistedInject.

• Multibinding setup for AssistedInject Factories

  Every ViewModel using AssistedInject needs a Factory interface annotated with @AssistedFactory. These factories are grouped together under a common parent type AssistedViewModelFactory to enable a Multibinding Dagger setup.

Example

• Create your ViewModel with an @AssistedInject constructor, an @AssistedFactory implementing AssistedViewModelFactory, and a companion object implementing MavericksViewModelFactory.

// NOTE: unlike using Jetpack ViewModels with Hilt, you do not need to annotate your ViewModel class with @HiltViewModel.
class MyViewModel @AssistedInject constructor(
  @Assisted initialState: MyState,
  // and other dependencies
) {

  @AssistedFactory
  interface Factory: AssistedViewModelFactory<MyViewModel, MyState> {
    override fun create(initialState: MyState): MyViewModel
  }

  companion object : MavericksViewModelFactory<MyViewModel, MyState> by hiltMavericksViewModelFactory()
}

• Tell Hilt to include your ViewModel's AssistedInject Factory in a Multibinding map.

@Module
@InstallIn(MavericksViewModelComponent::class)
interface ViewModelsModule {
    @Binds
    @IntoMap
    @ViewModelKey(HelloHiltViewModel::class)
    fun helloViewModelFactory(factory: HelloHiltViewModel.Factory): AssistedViewModelFactory<*, *>
}

• With this setup complete, request your ViewModel in a Fragment as usual, using any of Mavericks's ViewModel delegates.

class MyFragment : Fragment(), MavericksView {
  val viewModel: MyViewModel by fragmentViewModel()
}

How it works

HiltMavericksViewModelFactory will create a custom ViewModelComponent that is a child of SingletonComponent and will create an instance of your ViewModel with it.