Architecture and Patterns in Mobile Development: What They Are, Types, and How to Apply Them

Main Architectural Patterns

An architectural pattern determines how responsibilities are distributed among application classes. The choice of pattern affects how easy it is to add new screens and test code.

MVC (Model-View-Controller)

MVC is a classic pattern where Model handles data, View handles display, and Controller handles logic. In iOS, MVC is the default (UIViewController); in Android, Activity. The downside is that the Controller often becomes "massive" (Massive View Controller). According to an iOS developer survey (Reddit, 2025), 62% cite MVC as the main cause of unreadable code in legacy projects.

MVP (Model-View-Presenter)

MVP differs in that the Presenter manages the View through an interface, improving testability. MVP was popular in Android before Jetpack but lags behind MVVM in convenience.

MVVM (Model-View-ViewModel)

MVVM is Google's recommended pattern for Android and Apple's for iOS. The ViewModel stores state, and the View subscribes to changes via Data Binding or @Published. ViewModel does not depend on the View and is easy to test. At IT Sectr, we use MVVM as the main pattern in all projects.

MVI and VIPER

MVI is a reactive pattern where every action follows the Intent → Model → View cycle. MVI guarantees predictable state. VIPER is an iOS pattern with five layers (View, Interactor, Presenter, Entity, Router), providing maximum isolation but requiring a lot of boilerplate code.

Clean Architecture

Clean Architecture is Robert Martin's concept that divides an application into layers: outer layers (UI, DB, network) depend on inner layers (business logic, entities). In mobile development, Clean Architecture includes three layers: data (repositories), domain (Use Cases), and presentation (ViewModels, UI).

Repository Pattern is a key component of Clean Architecture, abstracting the data source. The repository decides whether to fetch data from the network or local storage (Room, Core Data) and returns a unified format. According to Google (Architecture Guide, 2025), Repository Pattern is recommended for any app with network requests. Clean Architecture is justified in projects with 3–5 screens or more — for simple apps, start with MVVM.

Creational Patterns

Singleton

Singleton is an architectural pattern that ensures a single instance of a class and provides a global access point to it. It is used for databases, settings managers, and caches. In Kotlin, it is created via object. The downside is that it complicates testing due to global state.

Factory and Builder

Factory delegates object creation to a factory method — instead of new, you call the factory. Builder is a step-by-step construction pattern for complex objects with many parameters (AlertDialog.Builder, NotificationCompat.Builder). Builder improves readability and allows objects to remain immutable after assembly.

Structural and Behavioral Patterns

Adapter, Facade, Delegate, Protocol

Adapter is an architectural pattern that converts the interface of one class into an interface expected by the client. In Android, this is RecyclerView.Adapter. Facade provides a simplified interface to a complex system — for example, a facade for an API that hides authentication details. Delegate is an iOS pattern where an object delegates a task (UITableViewDelegate). Protocol is Swift's equivalent of an interface.

Observer and Strategy

Observer is a subscription pattern for changes: the subject notifies subscribers of updates. In mobile development, Observer is the foundation of LiveData, StateFlow, RxJava, and Combine. Strategy is a pattern of interchangeable algorithms: you plug in a different strategy (sorting, validation) without multiple if-else statements.

Dependency Injection and State Management

Dependency Injection is an architectural pattern where an object receives its dependencies from outside instead of creating them itself. Instead of new Database(), you pass the database through the constructor. DI simplifies testing — you can use a Mock instead of a real database — and makes it easy to swap implementations. Popular DI frameworks: Dagger and Hilt (Android), Swinject (iOS), Koin (Kotlin). Hilt — a wrapper over Dagger recommended by Google — reduces DI setup by 3 times.

Service Locator is an alternative to DI with a central registry of dependencies. Simpler to implement, but it hides class dependencies, making testing harder. Modern projects prefer DI via Hilt or Koin.

State Management in Flutter

In Flutter, state management is its own ecosystem. Redux — a single Store with changes through Actions → Reducer → State. BLoC from Google separates events and states via Stream. Provider — a simple DI container recommended by Google for Flutter until 2023. Riverpod — an improved Provider that solves compilation and testing issues. GetX — a micro-framework with routing, DI, and state management. For beginner Flutter developers, we recommend Provider or Riverpod as the best-documented solutions.

SOLID and DRY Principles

Beyond specific patterns, there are general architecture design principles applicable in any language and framework.

SOLID — five principles of object-oriented design: Single Responsibility (one class — one task), Open-Closed (open for extension, closed for modification), Liskov Substitution (subclasses replace their parent), Interface Segregation (small interfaces), Dependency Inversion (depend on abstractions). In mobile development, SRP is the most useful principle: each class does only one thing. According to IT Sectr's experience, violating SRP is the cause of 70% of testing problems in commercial projects.

// Пример: нарушение SRP
class UserManager {
    fun saveUser(user: User) { /* сохранение */ }
    fun validateEmail(email: String): Boolean { /* валидация */ }
    fun sendEmail(user: User) { /* отправка */ }
    fun formatUser(user: User): String { /* форматирование */ }
}

// Исправление: разделяем на отдельные классы
class UserRepository { fun save(user: User) {} }
class EmailValidator { fun isValid(email: String): Boolean {} }
class EmailService { fun send(user: User) {} }
class UserFormatter { fun format(user: User): String {} }

The Kotlin example shows how we transform one UserManager class with four responsibilities into four classes with one responsibility each. Such code is easier to test, modify, and reuse.

DRY (Don't Repeat Yourself) — avoid code duplication. Extract repeated logic into shared methods or classes. KISS (Keep It Simple, Stupid) — simplicity is more important than elegance. YAGNI (You Aren't Gonna Need It) — don't write code for something that may not be needed. These principles help write clean, maintainable code without redundancy.

Android Platform Patterns

ViewModel (Android) is a Jetpack architecture component for storing UI state, resistant to screen rotation. ViewModel holds no references to Activity and is automatically cleared. LiveData — an observable data container with lifecycle awareness. StateFlow — a modern replacement for LiveData based on Kotlin Flow. SharedFlow — a Hot Flow for one-time events (navigation, toasts).

Data Binding and Two-Way Binding — mechanisms for binding UI and data in Android. Data Binding declares the connection in XML; Two-Way Binding automatically updates the field in the ViewModel. Unidirectional Data Flow — a principle where data flows in one direction: State → UI → Event → State. At IT Sectr, we use Unidirectional Data Flow in all new projects — it reduces the number of bugs caused by unexpected state changes.