Split generated AssistedInject_*Module to multiple modules

Currently the generated AssistedInject_*Module contains all the bindings for @AssistedInject.Factory annotated factories in one module. As a result, it’s impossible to have dependencies that exist only in subcomponents. For example:

I have two ViewModels, where one of them takes an argument (GithubApi in this case), which exists only in one the subcomponent hosting these view models.

class CommitDetailViewModel @AssistedInject constructor(
    @Assisted handle: SavedStateHandle,
    privatel val githubApi: GithubApi // Should be provided only in CommitDetailActivitySubcomponent
) : BaseViewModel(handle) {
    fun loadDetail() {
        Timber.v("Request commit detail")
        // use githubApi here
    }

    @AssistedInject.Factory
    interface Factory : ViewModelAssistedFactory<CommitDetailViewModel>
}

class CommitListViewModel @AssistedInject constructor(
    @Assisted handle: SavedStateHandle
) : BaseViewModel(handle) {

    fun loadCommits() {
        Timber.v("Request commit list")
    }

    @AssistedInject.Factory
    interface Factory : ViewModelAssistedFactory<CommitListViewModel>
}

interface ViewModelAssistedFactory<T : ViewModel> {
    fun create(handle: SavedStateHandle): T
}

@AssistedModule
@Module(includes = AssistedInject_ViewModelAssistedFactoriesModule.class)
public abstract class ViewModelAssistedFactoriesModule {
}

The generated AssistedInject_ViewModelAssistedFactoriesModule contains the bindings for both factories above. Due to that, I have to include it in the ApplicationComponent so it’s visible to my subcomponents. But then compilation fails since GithubApi’s binding is only defined in one of the subcomponents.

[davidliu]

Like I mentioned, the AssistedModule doesn’t impose a dependency requirement. You can put it in each of your components, and it will be fine. Declaring the AssistedModule in your app component won’t require you to have the MainRepo at the app level; you just also need to have the AssistedModule at the MainActivity level. Just try it out in code instead of trying to figure it out beforehand.

I’m not sure how to be any more clear in my explanation so I just made an example project for this:

https://github.com/davidliu/MultiLevelAssistedModule/tree/master/app/src/main/java/com/deviange/multilevelassistedmodule

[JakeWharton]

Today you can choose not to use @AssistedModule and specify the @Binds methods yourself in whichever modules you want. That’s not that far off from what you’re asking.

Ideally the @ContributesAndroidInjector mechanism would be generalized so we could have @ContributesAssistedFactory Foo.Factory foo() and it would do the right thing.