How i can add view model in module?

Question

In Dagger, how can I add a model to Module? For example I added the presenter in the following way:

@Module
class AboutModule(val appContext: Context) {

    @FragmentScope
    @Provides
    fun providePresenter(): AboutListContract.Presenter {
        return AboutListPresenter(appContext = appContext)
    }
}

Now i want want to add my View model, also with appContext.

class AboutViewModel(val appContext: Context): ViewModel() {

UPDATE: Can i add my view model smth like this?

@Module

    class AboutModule(val appContext: Context) {

        @FragmentScope
        @Provides
        fun provideModel(model: AboutViewModel): ViewModel {
            return AboutViewModel(appContext = appContext)
        }
    }

score 1 · Accepted Answer · edited Jul 28 '23 at 22:15

I solved my problem with next solution:

@Module
class AboutModule(val appContext: Context) {
    
    @FragmentScope
    @Provides
    fun provideFactory(): AboutViewModelFactory {
        return AboutViewModelFactory(appContext)
    }
}

And in fragment write smth like this:

class AboutFragment : BaseFragment(), OnItemClickListener {

    lateinit var viewModel: AboutViewModel
    @Inject lateinit var viewModelFactory: AboutViewModelFactory

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        injectDependencies()

        viewModel = ViewModelProviders
            .of(this, viewModelFactory)
            .get(AboutViewModel::class.java)
    }

    private fun injectDependencies() {
        activity?.let {
            DaggerAboutComponent.builder().aboutModule(AboutModule(it)).build().inject(this)
        }
    }
}

Nice advise: https://stackoverflow.com/a/60884492/6387618

score 1 · Answer 2 · answered Jun 22 '20 at 12:44

To retrieve the ViewModel from the component without Map Multibinding, you can do:

@Singleton
@Component(modules=[...])
interface SingletonComponent {
    val aboutListViewModel: Provider<AboutListViewModel>
}

Which works when you can use @Inject constructor:

// unscoped
class AboutListViewModel @Inject constructor(): ViewModel() {
}

Because now you can do:

class AboutListFragment: Fragment(R.layout.about_list_fragment) {
    private val viewModel by viewModels<AboutListViewModel>() {
        object: ViewModelProvider.Factory {
            override fun create(clazz: Class<ViewModel>) {
                return (requireActivity().application as MyApplication).component.aboutListViewModel.get()
            }
        }
    }
}

Which might seem tacky, but you can hide all of that in an extension function

fun <T: ViewModel> Fragment.fragmentViewModels(viewModelCreator: SingletonComponent.() -> T) = viewModels<T> {
    object: ViewModelProvider.Factory {
        override fun create(clazz: Class<ViewModel>) {
            val component = requireActivity().application as MyApplication).component
            return viewModelCreator(component)
        }
    }
}

Because now you can do

class AboutListFragment: Fragment(R.layout.about_list_fragment) {
    private val viewModel by fragmentViewModels<AboutListViewModel> { component ->
        component.aboutListViewModel().get()
    }
}

And this would work even without map multibinding. If you need a SavedStateHandle, you'd need AssistedInject, but if you don't want that, it'll be easier when Dagger-Hilt is stable (then it'll be as simple as @ViewModelInject and @Assisted).

score 0 · Answer 3 · answered Mar 27 '20 at 10:49

0

ViewModels are injected using Dagger Multibindings

refer to this medium article: https://medium.com/chili-labs/android-viewmodel-injection-with-dagger-f0061d3402ff

context can be injected by providing in the AppModule class.

answered Mar 27 '20 at 10:49

Nataraj KR

1,001
10
22

There is no reason to use map multibinding for injecting ViewModels. – EpicPandaForce May 31 '20 at 08:22
@EpicPandaForce is there any other way to inject all viewmodels into the viewmodel factory? – Nataraj KR Jun 22 '20 at 06:42
You don't really need 1 ViewModelProvider.Factory in order to use N ViewModels. But if you're using Hilt the map multibinding is automatic, but it also overrides the default ViewModelProvider.Factory so it's more convenient. – EpicPandaForce Jun 22 '20 at 07:45
@EpicPandaForce yeah with Hilt it is obvious. Can you please explain how viewmodel factory isn't required in the case of dagger? – Nataraj KR Jun 22 '20 at 08:06
I don't see why "you don't need to use map multibinding" translates to "you don't need ViewModelProvider.Factory". – EpicPandaForce Jun 22 '20 at 08:38
@EpicPandaForce please give your solution for us to understand – Nataraj KR Jun 22 '20 at 12:06
sure, let's do that – EpicPandaForce Jun 22 '20 at 12:45

How i can add view model in module?

3 Answers3

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