Inject ViewModel using Dagger 2 + Kotlin + ViewModel

Question

class SlideshowViewModel : ViewModel() {

@Inject lateinit var mediaItemRepository : MediaItemRepository

fun init() {
    What goes here?
}

So I\'m tr

Answer 1

Refer to a repo I created when I was learning dagger+kotlin

Essentially you need a ViewModelFactory instance to the UI layer, you use that to create a viewmodel.

@AppScope
class ViewModelFactory
@Inject
constructor(private val creators: Map, @JvmSuppressWildcards Provider>)
    : ViewModelProvider.Factory {


    @SuppressWarnings("Unchecked")
    override fun  create(modelClass: Class): T {
        var creator = creators[modelClass]

        if (creator == null) {
            for (entry in creators) {
                if (modelClass.isAssignableFrom(entry.key)) {
                    creator = entry.value
                    break
                }
            }
        }

        if (creator == null) throw IllegalArgumentException("Unknown model class" + modelClass)

        try {
            return creator.get() as T
        } catch (e: Exception) {
            throw RuntimeException(e)
        }
    }
}

Your ViewModelModule should look like (this is where you store all viewmodels).

@Module
abstract class ViewModelModule {
    @AppScope
    @Binds
    @IntoMap
    @ViewModelKey(YourViewModel::class)
    abstract fun bindsYourViewModel(yourViewModel: YourViewModel): ViewModel

    // Factory
    @AppScope
    @Binds abstract fun bindViewModelFactory(vmFactory: ViewModelFactory): ViewModelProvider.Factory
}

Then create a dagger map key

@Documented
@Target(AnnotationTarget.FUNCTION)
@Retention(AnnotationRetention.RUNTIME)
@MapKey
internal annotation class ViewModelKey(val value: KClass)

Then on your UI layer, inject the factory and instantiate your viewmodel using ViewModelProviders

class YourActivity : BaseActivity() {
    @Inject
    lateinit var viewModelFactory: ViewModelProvider.Factory

    lateinit var yourViewModel: YourViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        ...
        ...
        (application as App).component.inject(this)
    }

    override fun onStart() {
        super.onStart()
        yourViewModel = ViewModelProviders.of(this, viewModelFactory).get(YourViewModel::class.java)

        // you can now use your viewmodels properties and methods
        yourViewModel.methodName() 
        yourViewModel.list.observe(this, { ... })

    }