Level 9

The Full Network Stack (Retrofit + Repository)

Clean Architecture Data Layer

The "Clean Architecture" way to fetch data.

📚 Explanation

Clean Architecture separates concerns: API (Retrofit interface), Repository (data source abstraction), and ViewModel (business logic). Retrofit uses suspend functions for coroutines. `stateIn` converts a Flow to a StateFlow, sharing the subscription across collectors.

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kotlin

// The Interface (API)
import retrofit2.http.GET

interface UserService {
    @GET("users/me")
    suspend fun getUser(): UserDto // Suspend function for Coroutines
}

// The Repository (Data Source)
import javax.inject.Inject

class UserRepository @Inject constructor(
    private val api: UserService
) {
    // Expose a Flow, or a suspend function
    fun getUserStream(): Flow<User> = flow {
        emit(api.getUser().toDomain())
    }
}

// The Consumption (ViewModel)
@HiltViewModel
class MainViewModel @Inject constructor(
    private val repository: UserRepository
) : ViewModel() {
    
    val userState = repository.getUserStream()
        .stateIn(
            scope = viewModelScope,
            started = SharingStarted.WhileSubscribed(5000),
            initialValue = User.Empty
        )
}

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