mlykotom

class SomeViewModel(
  private val dep1: Dependency,
  private val dep2: Dependency2,
  private val articleId: String 
) : ViewModel() {
  
class Factory constructor(
    private val dep1: Dependency,
    private val dep2: Dependency2,
    private val articleId: String 

mlykotom

/**
 * Base interface for all ViewModel factories
 */
interface AssistedSavedStateViewModelFactory<T : ViewModel> {
   fun create(savedStateHandle: SavedStateHandle): T
}

mlykotom

class SomeViewModel(/* ..ommited.. */){
  val counter = savedStateHandle.getLiveData("counter", 0)

  fun onPlusClick() {
    counter.value = (counter.value ?: 0) + 1
  }
}

mlykotom

class SomeViewModel(/* ..ommited.. */){
  val counter = MutableLiveData<Int>(0)

  init {
    counter.value = savedStateHandle.get("counter") ?: 0
    
    counter.observeForever { newValue ->
      savedStateHandle.set("counter", newValue)
    }
  }

mlykotom

class SomeViewModel(
   private val application: Application,
   private val savedStateHandle: SavedStateHandle
){
  // ...
}

mlykotom

class SomeFragment : Fragment() {
  
  lateinit var viewModel : SomeViewModel
  
  override fun onCreate(savedState: Bundle?){
    super.onCreate(savedState)    
    // default arguments, so you can set something dynamically
    val defaultArgs: Bundle? = bundleOf("id" to 5) // may be null
    
    // default factory for ViewModel creation

mlykotom

class SomeViewModel @Inject constructor(
  private val depFromDagger1: Dependency,
  private val depFromDagger2: Dependency2
) : ViewModel(){
  
  // may crash with UninitializedPropertyAccessException
  lateinit var articleId: String
  
  // must !! or ?. for every access
  var fragmentParams: Bundle? = null

mlykotom

class SomeFragment : Fragment() {
  
  // inject into this class omitted for brevity
  
  @Inject
  lateinit var dep1: Dependency
  @Inject
  lateinit var dep2: Dependency
  
  lateinit var viewModel : SomeViewModel

mlykotom

class SomeViewModel @AssistedInject constructor(
    private val appContext: Context,
    private val someDaggerDependency: SomeDaggerDependency,
    @Assisted private val savedStateHandle: SavedStateHandle
) : ViewModel() {
    @AssistedInject.Factory
    interface Factory : AssistedSavedStateViewModelFactory<SomeViewModel>
}

mlykotom

@Reusable
class InjectingSavedStateViewModelFactory @Inject constructor(
    private val assistedFactories: Map<Class<out ViewModel>, @JvmSuppressWildcards AssistedSavedStateViewModelFactory<out ViewModel>>
) {
    fun create(owner: SavedStateRegistryOwner, defaultArgs: Bundle? = null): AbstractSavedStateViewModelFactory {
        return object : AbstractSavedStateViewModelFactory(owner, defaultArgs) {
          
            @Suppress("UNCHECKED_CAST")
            override fun <T : ViewModel?> create(key: String, modelClass: Class<T>, handle: SavedStateHandle): T {
                // Attempt to get ViewModel from assisted inject factories