Architectural Patterns in Kotlin: MVC, MVP, MVVM, and MVI

How Not to Drown in Chaos: Architectural Patterns in Kotlin

Have you ever opened your project a month after writing it and couldn't figure out where the authorization logic is? Or tried to add a new button, and it broke the list functionality? Sound familiar? Welcome to the world of applications without architecture.

Architectural patterns in Kotlin are not a tribute to fashion or abstract theories. They are salvation from "spaghetti code," where everything is mixed together: business logic, UI, network operations, and database work. In this article, we will cover four main patterns: MVC, MVP, MVVM, and MVI. You will see them in action with real Kotlin examples, understand the key differences, and be able to choose the right tool for your task. Let's go!

What is an Architectural Pattern and Why Do You Need It?

An architectural pattern is the skeleton of your application. It dictates how classes communicate with each other, where to store data, and who is responsible for display. Without it, sooner or later you will get a God Object — a class that does everything. Or Callback Hell — when one callback spawns another, and the code becomes unreadable.

Kotlin, with its concise syntax and null safety, is ideal for clean architecture. But the language is only half the story. The other half is choosing the right pattern.

MVC (Model-View-Controller) — The Classic

The oldest and simplest pattern. Its essence:

• Model — data and business logic.
• View — display (Activity, Fragment, Compose).
• Controller — the connecting link, handles user input.

In Kotlin (especially for Android), MVC often turns into a "Fat Controller." The Activity becomes both View and Controller simultaneously. Example:

// Bad: Activity is both View and Controllerclass LoginActivity : AppCompatActivity() {    private lateinit var emailEditText: EditText    private lateinit var passwordEditText: EditText

    override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        setContentView(R.layout.activity_login)

        // Controller logic right here        findViewById<Button>(R.id.loginButton).setOnClickListener {            val email = emailEditText.text.toString()            val password = passwordEditText.text.toString()            // Validation and API call — all in one place            if (email.isNotEmpty() && password.isNotEmpty()) {                loginUser(email, password)            }        }    }

    private fun loginUser(email: String, password: String) {        // Network work — directly in Activity        CoroutineScope(Dispatchers.IO).launch {            val result = api.login(email, password)            withContext(Dispatchers.Main) {                // UI update — also here                Toast.makeText(this@LoginActivity, result.message, Toast.LENGTH_SHORT).show()            }        }    }}

Pros: simplicity, low entry barrier.

Cons: View and Controller are tightly coupled. Testing logic without an Android emulator is impossible. For large projects — a nightmare.

MVP (Model-View-Presenter) — Separation of Powers

MVP solves the main problem of MVC: View is separated from logic through interfaces. The Presenter is the "brain" that knows nothing about Android. The View is a passive layer.

Example in Kotlin:

// Interfaces for communicationinterface LoginView {    fun showLoading()    fun hideLoading()    fun showError(message: String)    fun navigateToHome()}

class LoginPresenter(private val view: LoginView, private val authRepository: AuthRepository) {

    fun login(email: String, password: String) {        view.showLoading()        CoroutineScope(Dispatchers.IO).launch {