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Dagger 2 AssistedInject ViewModels
import com.squareup.inject.assisted.dagger2.AssistedModule
import dagger.Module
@AssistedModule
@Module(includes = [AssistedInject_AssistedInjectModule::class])
class AssistedInjectModule
class SomeFragment : Fragment() {
private lateinit var component: Component
private lateinit var someViewModel: SomeViewModel
override fun onAttach(context: Context) {
super.onAttach(context)
component = (context.applicationContext as App).component
component.inject(this)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val someViewModel: SomeViewModel by navGraphSavedStateViewModels(R.id.nav_graph) { handle ->
component.someViewModelFactory().create(
coroutineDispatcherProvider = DefaultDispatcherProvider(),
someStringVal = "Some string value"
)
}
this.someViewModel = someViewModel
...
return binding.root
}
}
class SomeViewModel @AssistedInject constructor(
@Assisted private val coroutineScopeProvider: CoroutineScope?,
@Assisted private val coroutineDispatcherProvider: DispatcherProvider,
@Assisted private val someStringVal: String,
private val repository: SomeRepository
) : ViewModel() {
@AssistedInject.Factory
interface Factory {
fun create(
coroutineScopeProvider: CoroutineScope? = null,
coroutineDispatcherProvider: DispatcherProvider,
someStringVal: String
): FeedViewModel
}
private val coroutineScope = getViewModelScope(coroutineScopeProvider)
}
package app.topcafes.dependencyinjection
import android.os.Bundle
import androidx.annotation.IdRes
import androidx.fragment.app.Fragment
import androidx.fragment.app.createViewModelLazy
import androidx.lifecycle.AbstractSavedStateViewModelFactory
import androidx.lifecycle.SavedStateHandle
import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelProvider
import androidx.lifecycle.viewModelScope
import androidx.navigation.fragment.findNavController
import androidx.savedstate.SavedStateRegistryOwner
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
/**
* See 'Dagger Tips' > 'Injecting ViewModel + SavedStateHandle'
* [https://proandroiddev.com/dagger-tips-leveraging-assistedinjection-to-inject-viewmodels-with-savedstatehandle-and-93fe009ad874#7919]
* Original: [https://gist.github.com/Zhuinden/06b86cb35cba0cb5e880505042e18c3d]
* Author: Gabor Varadi [https://twitter.com/Zhuinden]
*/
/**
* Create a single instance of the ViewModel with Saved State enabled.
*
* @receiver Fragment launches ViewModel
* @param creator Function1<SavedStateHandle, T>
* @return Lazy<T>
*/
inline fun <reified T : ViewModel> Fragment.fragmentSavedStateViewModels(
crossinline creator: (SavedStateHandle) -> T
): Lazy<T> {
return createViewModelLazy(
viewModelClass = T::class,
storeProducer = { viewModelStore },
factoryProducer = {
createAbstractSavedStateViewModelFactory(
arguments = arguments ?: Bundle(),
creator = creator
)
})
}
/**
* Create a shared ViewModel instance across a given navGraphId.
*
* @receiver Fragment launches ViewModel
* @param navGraphId Int defines ViewModel lifecycle
* @param creator Function1<SavedStateHandle, T>
* @return Lazy<T>
*/
inline fun <reified T : ViewModel> Fragment.navGraphSavedStateViewModels(
@IdRes navGraphId: Int,
crossinline creator: (SavedStateHandle) -> T
): Lazy<T> {
// Wrapped in lazy to not search the NavController each time we want the backStackEntry
val backStackEntry by lazy { findNavController().getBackStackEntry(navGraphId) }
return createViewModelLazy(
viewModelClass = T::class,
storeProducer = { backStackEntry.viewModelStore },
factoryProducer = {
backStackEntry.createAbstractSavedStateViewModelFactory(
arguments = backStackEntry.arguments ?: Bundle(),
creator = creator
)
})
}
/**
* Helper factory function to create a single instance of the ViewModel.
*
* @receiver SavedStateRegistryOwner
* @param arguments Bundle?
* @param creator Function1<SavedStateHandle, T>
* @return ViewModelProvider.Factory
*/
inline fun <reified T : ViewModel> SavedStateRegistryOwner.createAbstractSavedStateViewModelFactory(
arguments: Bundle,
crossinline creator: (SavedStateHandle) -> T
): ViewModelProvider.Factory {
return object : AbstractSavedStateViewModelFactory(this, arguments) {
@Suppress("UNCHECKED_CAST")
override fun <T : ViewModel?> create(
key: String,
modelClass: Class<T>,
handle: SavedStateHandle
): T = creator(handle) as T
}
}
/**
* Configure CoroutineScope injection for production and testing.
*
* @receiver ViewModel provides viewModelScope for production
* @param coroutineScope null for production, injects TestCoroutineScope for unit tests
* @return CoroutineScope to launch coroutines on
*/
fun ViewModel.getViewModelScope(coroutineScope: CoroutineScope?) =
if (coroutineScope == null) this.viewModelScope
else coroutineScope
/**
* Configure Dispatchers injection for production and testing.
*
* See 'Unit Testing Coroutine Suspend Functions using TestCoroutineDispatcher' > 'DispatcherProvider'
* [https://craigrussell.io/2019/11/unit-testing-coroutine-suspend-functions-using-testcoroutinedispatcher/#dispatcherprovider]
* Author: Craig Russell [https://twitter.com/trionkidnapper]
*/
interface DispatcherProvider {
fun main(): CoroutineDispatcher = Dispatchers.Main
fun default(): CoroutineDispatcher = Dispatchers.Default
fun io(): CoroutineDispatcher = Dispatchers.IO
fun unconfined(): CoroutineDispatcher = Dispatchers.Unconfined
}
class DefaultDispatcherProvider : DispatcherProvider
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