Clean-Architecture

Welcome to Part 4 of our KMP series — Build a Real App. In the next four tutorials, we build a complete cross-platform Notes app from scratch. This article covers the planning phase: architecture decisions, tech stack, project structure, and the initial setup that makes everything work on both Android and iOS. By the end of this tutorial, you will have a working project skeleton with shared business logic, a SQLDelight database, Koin dependency injection, and basic UI on both platforms. ...

You have learned Ktor for networking, SQLDelight for databases, Koin for dependency injection, and shared ViewModels. You have all the building blocks. But how do you organize them? Without structure, your project becomes a mess. Networking code mixed with UI logic. Database queries inside ViewModels. Platform code scattered everywhere. Clean Architecture solves this. It gives you clear layers with clear rules about what goes where and what can depend on what. ...

In the previous tutorial, we planned our task manager app. Now we build the foundation — the data layer. The data layer is everything below the UI: the database, the repository, and the use cases. Get this right, and the UI layer writes itself. What We Build in This Tutorial data/ ├── local/ │ ├── TaskEntity.kt ← Database table definition │ ├── TaskDao.kt ← Database operations │ └── AppDatabase.kt ← Room database ├── mapper/ │ └── TaskMapper.kt ← Convert Entity ↔ Domain Model ├── repository/ │ └── TaskRepositoryImpl.kt ← Repository implementation │ domain/ ├── model/ │ ├── Task.kt ← Clean domain model │ ├── Category.kt ← Enum │ └── Priority.kt ← Enum ├── repository/ │ └── TaskRepository.kt ← Interface (contract) └── usecase/ ├── GetTasksUseCase.kt ├── AddTaskUseCase.kt ├── ToggleTaskUseCase.kt └── DeleteTaskUseCase.kt Step 1: Domain Models The domain layer is pure Kotlin — no Android dependencies, no Room annotations. This is the “truth” of your app. ...

You have learned every piece: layouts, state, navigation, ViewModel, MVI, Room, Hilt, animations, testing, and adaptive layouts. Now it is time to use them all together. In the next five tutorials, we will build a complete task manager app from scratch. Not a toy demo — a real app with real architecture that you could publish to Google Play. This tutorial is about planning — deciding what to build, how to organize the code, and what dependencies to use. No code yet. Just decisions. ...