compose-architecture

Android Architecture

Modularization

app/                            // app entry, nav graph
build-logic/                    // convention plugins (optional)
core/
  designsystem/                 // theme, tokens, shared composables
  domain/                       // pure Kotlin business types, no Android deps
  data/                         // repositories, data sources
  network/                      // Ktor / Retrofit setup
  database/                     // Room entities, DAOs
feature/
  home/                         // self-contained screen modules
  profile/
  settings/

Each feature module exposes a Route composable and a nav declaration. The app module wires them into the nav graph.

Repository pattern

// feature/profile/data/ProfileRepository.kt
interface ProfileRepository {
    suspend fun getUser(id: String): User
    fun observeUser(id: String): Flow<User>
}

class DefaultProfileRepository @Inject constructor(
    private val remote: ProfileRemoteDataSource,
    private val local: ProfileLocalDataSource,
) : ProfileRepository {

    override suspend fun getUser(id: String): User {
        val cached = local.get(id)
        if (cached != null) return cached
        val fresh = remote.fetch(id)
        local.put(fresh)
        return fresh
    }

    override fun observeUser(id: String): Flow<User> = local.observe(id)
}

Rules:

• Repository is an interface; bind the default via Hilt.
• Data sources are package-private inside the data module - the repo is the only public contract.
• Suspend functions for one-shot reads, Flow<T> for observable streams.

ViewModel patterns

@HiltViewModel
class ProfileViewModel @Inject constructor(
    private val repo: ProfileRepository,
    savedState: SavedStateHandle,
) : ViewModel() {

    private val args = savedState.toRoute<Profile>()

    val state: StateFlow<ProfileUiState> = repo.observeUser(args.userId)
        .map { ProfileUiState.Success(it) as ProfileUiState }
        .catch { emit(ProfileUiState.Error(it.message ?: "Unknown")) }
        .stateIn(
            scope = viewModelScope,
            started = SharingStarted.WhileSubscribed(5_000),
            initialValue = ProfileUiState.Loading,
        )

    fun onIntent(intent: ProfileIntent) {
        when (intent) {
            ProfileIntent.Refresh -> viewModelScope.launch { repo.refresh(args.userId) }
        }
    }
}