如何使用 Dagger2 为 Android 提供 Room Dao 依赖项？

Question

My repository passes in a Room Persistence lib. Dao object as a dependency. The problem is Dao is an interface. The most recent suggestion by Google is to do the following:

// Tells Dagger this is a Dagger module
// Because of @Binds, StorageModule needs to be an abstract class
@Module
abstract class StorageModule {

    // Makes Dagger provide SharedPreferencesStorage when a Storage type is requested
    @Binds
    abstract fun provideStorage(storage: SharedPreferencesStorage): Storage
}

In the example above, SharedPreferencesStorage is a user created implementation of the interface, Storage . The problem with Room dao dependencies is that the implementation is generated by the library like roomDatabase.getDatabase(context).myDao() . The most recent Dagger version seems to avoid using the old way of passing in component dependencies through a module constructor. Is there a way to do this using @Subcomponent.Factory or @Component.Factory , or is the "old" way the only way to do this for Room dao dependencies?

Answer 1

You could try the following approach:

@Module
class DatabaseModule {
    @Provides
    fun provideDaoA(db: MyDb): DaoA = db.daoA()

    @Provides
    fun provideDaoB(db: MyDb): DaoB = db.daoB()
}

class MyRepository @Inject constructor(private val daoA: DaoA) {..}

Another approach from googlesamples :

    @JvmStatic
    @Singleton
    @TasksLocalDataSource
    @Provides
    fun provideTasksLocalDataSource(
        database: ToDoDatabase,
        ioDispatcher: CoroutineDispatcher
    ): TasksDataSource {
        return TasksLocalDataSource(
            database.taskDao(), ioDispatcher
        )
    }