App Architecture Skill

Quick Start

MVVM Pattern

@HiltViewModel
class UserViewModel @Inject constructor(
    private val repository: UserRepository
) : ViewModel() {
    private val _state = MutableLiveData<UiState>()
    val state: LiveData<UiState> = _state
    
    fun loadUser(id: Int) {
        viewModelScope.launch {
            _state.value = repository.getUser(id)
        }
    }
}

Repository Pattern

interface UserRepository {
    suspend fun getUser(id: Int): User
}

class UserRepositoryImpl(
    private val dao: UserDao,
    private val api: UserApi
) : UserRepository {
    override suspend fun getUser(id: Int): User {
        return dao.getUser(id) ?: api.fetchUser(id)
    }
}

Dependency Injection (Hilt)

@Module
@InstallIn(SingletonComponent::class)
object RepositoryModule {
    @Provides
    fun provideUserRepository(dao: UserDao, api: UserApi): UserRepository {
        return UserRepositoryImpl(dao, api)
    }
}

Key Concepts

MVVM Benefits

• Lifecycle awareness
• Configuration change handling
• Separation of concerns
• Testability

Clean Architecture Layers

• Domain: Business rules
• Application: Use cases
• Presentation: UI
• Infrastructure: Data sources

SOLID Principles

• S: Single Responsibility
• O: Open/Closed
• L: Liskov Substitution
• I: Interface Segregation
• D: Dependency Inversion

Best Practices

✅ Dependency injection ✅ Interface-based design ✅ Layered architecture ✅ Single responsibility ✅ Testable code

Resources

• Architecture Guide
• SOLID Principles
• Hilt Documentation