Hilt 注入子类作为父类型

Question

我有 3 个存储库：

interface MainRepository {
        ...
    }

interface LocalRepository {
        ...
    }

interface WebRepository {
        ...
    }

每个存储库都有自己的实现：

@Singleton
class MainRepositoryImpl @Inject constructor(
    private val localRepository: LocalRepository,
    private val webRepository: WebRepository
) : MainRepository {
...
}

@Singleton
class LocalRepositoryImpl @Inject constructor(
    private val localMapper: LocalMapper
    private val popularMovieDao: PopularMovieDao
) : LocalRepository {
...
}

@Singleton
class WebRepositoryImpl @Inject constructor(
    private val webMapper: WebMapper,
    private val popularMovieApi: PopularMovieApi
) : WebRepository {
...
}

如您所见，MainRepository 需要将其他两个存储库都注入其中，但是，我真的不知道该怎么做。

当然，我可以使用 LocalRepositoryImpl 或 WebRepositoryImpl 类型注入它，但我想使用 LocalRepository 或 WebRepository 类型注入它以获得更通用的方法。

这是我尝试编写的模块：

@InstallIn(ApplicationComponent::class)
@Module
object Module {

    @Singleton
    @Provides
    fun provideWebRepository(): WebRepository {
        return WebRepositoryImpl(mapper = WebMapper(), popularMovieApi = PopularMovieApi.getInstance())
    }

    @Singleton
    @Provides
    fun provideLocalRepository(): LocalRepository {
        return LocalRepositoryImpl(mapper = LocalMapper(), // Here I can't really 
            // figure out how to get @Dao since it requires DB 
            // which requires context and etc 
            // which makes me think that I've got completely wrong approach to this)
    }
}

我的 LocalData 模块：

@InstallIn(ApplicationComponent::class)
@Module
object LocalDataSourceModule {
    @Singleton
    @Provides
    fun provideMainDatabase(@ApplicationContext context: Context): MainDatabase = MainDatabase.getInstance(context)

    @Provides
    fun providePopularMovieDao(mainDatabase: MainDatabase): PopularMovieDao = mainDatabase.popularMovieDao()
}

我的 WebData 模块：

@InstallIn(ApplicationComponent::class)
@Module
object RemoteDataSourceModule {

    @Singleton
    @Provides
    fun providePopularMovieApi(): PopularMovieApi = PopularMovieApi.getInstance()
}

如何在维护接口类型（LocalRepository 和`WebRepository）的同时正确地注入我拥有的实现（LocalRepositoryImpl 和WebRepositoryImpl）？？

Answer 1

使用@Binds。而不是你的object Module 使用以下模块：

@InstallIn(ApplicationComponent::class)
@Module
interface Module {

    @Binds
    fun bindWebRepository(repository: WebRepositoryImpl): WebRepository

    @Binds
    fun bindLocalRepository(repository: LocalRepositoryImpl): LocalRepository
}

它告诉 Dagger 如果你需要 WebRepository 依赖，那么它必须提供 WebRepositoryImpl 并且对于 LocalRepository 和 LocalRepositoryImpl 也是如此。

What is the use case for @Binds vs @Provides annotation in Dagger2

Answer 2

您的存储库

interface MainRepository {
        ...
}

interface LocalRepository {
        ...
}

interface WebRepository {
        ...
}

实现（这里没有@Inject 或@Singleton！）

class MainRepositoryImpl constructor(
    private val localRepository: LocalRepository,
    private val webRepository: WebRepository
) : MainRepository {
...
}


class LocalRepositoryImpl constructor(
    private val localMapper: LocalMapper
    private val popularMovieDao: PopularMovieDao
) : LocalRepository {
...
}


class WebRepositoryImpl constructor(
    private val webMapper: WebMapper,
    private val popularMovieApi: PopularMovieApi
) : WebRepository {
...
}

Di.Module（存储库模块）

@Module
@InstallIn(ApplicationComponent::class)
object RepositoryModule {
    
 @Singleton
 @Provides
 fun provideMainRepository(
           localRepository: LocalRepository,
           webRepository: WebRepository
 ): MainRepository = MainRepositoryImpl(localRepository, webRepository)

 @Singleton
 @Provides
 fun provideLocalRepository(
        localMapper: LocalMapper,
        popularMovieDao: PopularMovieDao
 ): LocalRepository = LocalRepositoryImpl(localMapper, popularMovieDao)

 @Singleton
 @Provides
 fun provideWebRepository(
        webMapper: WebMapper,
        popularMovieApi: PopularMovieApi
 ): WebRepository = WebRepositoryImpl(webMapper, popularMovieApi)

试试这个，告诉我它是否有效。由于您已使用 @Provides 提供了所有存储库，因此 Dagger-Hilt 知道如何创建它们。您是否在本地数据库中使用Room？如果是，那么像您那样创建数据库可能不正确。如果您不使用Room，您应该开始使用它，因为它让您的生活更轻松。

下面是用匕首创建房间数据库的正确方法：

实体模块

@Entity(tableName = "exampleTableName")
data class ExampleEntity(
    @PrimaryKey(autoGenerate = true)
    val id: Int,
    // ... whatever you need
    val header: String = "",
    val title: String = "",
    val description: String = "",
)

示例数据库

@Database(entities = [ExampleEntity::class], version = 1)
abstract class ExampleDatabase : RoomDatabase() {
    abstract fun exampleDao(): ExampleDao

    companion object {
        const val DATABASE_NAME = "example_db"
    }
}

DAO

@Dao
interface DocumentDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insert(exampleEntity: List<ExampleEntity>)

    @Query("SELECT * FROM exampleTableName")
    suspend fun getList(): List<ExampleEntity>
}

房间分区模块

@Module
@InstallIn(ApplicationComponent::class)
object RoomModule {

    @Singleton
    @Provides
    fun provideExampleDB(@ApplicationContext context: Context): ExampleDatabase = Room.databaseBuilder(
        context,
        ExampleDatabase::class.java,
        ExampleDatabase.DATABASE_NAME,
    ).fallbackToDestructiveMigration().build()

    @Singleton
    @Provides
    fun provideExampleDAO(exampleDatabase: ExampleDatabase): ExampleDao = exampleDatabase.exampleDao()

  }