🧱 Does Clean Architecture Really Scale in iOS Development?

Clean Architecture promises maintainability, testability, and long-term scalability. While it's often effective on the backend or in enterprise-scale systems, applying it as-is in mobile — especially iOS/SwiftUI projects — can become more of a burden than a benefit.

Let’s take a deep dive into where it struggles and how we can evolve it for modern mobile development.

🚧 Where Clean Architecture Falls Short in iOS

1. Too Many Layers, Too Little Value

Fetching something as simple as user data ends up involving 6–7 separate files and protocols. Let’s walk through a typical Clean Architecture implementation:

✅ Fetching User Data with Clean Architecture

// 1. Entity
struct User {
    let id: String
    let name: String
    let email: String
}

// 2. DTO
struct UserDTO: Decodable {
    let id: String
    let name: String
    let email: String

    func toDomain() -> User {
        User(id: id, name: name, email: email)
    }
}

// 3. Repository Protocol
protocol UserRepository {
    func fetchUser() async throws -> User
}

// 4. Repository Implementation
final class UserRepositoryImpl: UserRepository {
    private let service: NetworkService

    init(service: NetworkService) {
        self.service = service
    }

    func fetchUser() async throws -> User {
        let dto: UserDTO = try await service.request(endpoint: "/user")
        return dto.toDomain()
    }
}

// 5. UseCase
protocol FetchUserUseCase {
    func execute() async throws -> User
}

final class FetchUserUseCaseImpl: FetchUserUseCase {
    private let repository: UserRepository

    init(repository: UserRepository) {
        self.repository = repository
    }

    func execute() async throws -> User {
        return try await repository.fetchUser()
    }
}

// 6. ViewModel
@MainActor
final class ProfileViewModel: ObservableObject {
    @Published var user: User?

    private let fetchUserUseCase: FetchUserUseCase

    init(fetchUserUseCase: FetchUserUseCase) {
        self.fetchUserUseCase = fetchUserUseCase
    }

    func loadUser() async {
        do {
            user = try await fetchUserUseCase.execute()
        } catch {
            print("Error: \(error)")
        }
    }
}        

🧠 The Problem?

• It's overkill for most iOS use cases
• Slows down onboarding and development
• Adds unnecessary boilerplate
• Goes against the simplicity and declarative nature of SwiftUI

💡 The Pragmatic, Lightweight Approach

Let’s streamline the architecture while keeping testability and separation of concerns.

🔁 The Leaner Way (with SwiftUI in Mind)

@MainActor
final class ProfileViewModel: ObservableObject {
    @Published var user: User?

    private let service = NetworkService()

    func loadUser() async {
        do {
            let dto: UserDTO = try await service.request(endpoint: "/user")
            user = dto.toDomain()
        } catch {
            print("Error: \(error)")
        }
    }
}        

We eliminated the repository, use case, and interface layers. Yet the ViewModel remains testable, simple, and effective.

🧪 What About Testing?

No worries — you still can (and should) write unit tests:

func testUserMapping() {
    let dto = UserDTO(id: "123", name: "Ufuk", email: "ufuk@example.com")
    let user = dto.toDomain()
    
    XCTAssertEqual(user.name, "Ufuk")
}        

Test coverage doesn’t have to suffer for the sake of simplicity.

✅ Practical Advice

🔸 Don’t be dogmatic — architecture should serve the project, not the other way around. 🔸 Embrace SwiftUI’s reactive nature, not fight it with imperative overload. 🔸 Introduce UseCases only when there’s real business logic. 🔸 Let each module own its domain, especially in modular apps.

📌 Real-World Example: Horizon SuperApp

While working on Horizon SuperApp — a large modular SwiftUI application — we started with a classic Clean Architecture setup. Over time, we faced:

• Slower development speed
• Over-engineered layers
• Increased cognitive load for new team members

Eventually, we adopted a leaner, more reactive, and SwiftUI-native approach — keeping core principles, but removing excessive abstractions.

🧠 Conclusion

Clean Architecture is a powerful concept — but not a silver bullet. On iOS, especially with SwiftUI, you’re often better off with pragmatic adaptations that serve your app’s complexity, team size, and goals.

💬 How About You?

Have you implemented Clean Architecture in your iOS apps? Did it scale well? Or did you switch to a simpler, more efficient design?

I'd love to hear your thoughts 👇

🧠 #iOSDevelopment #SwiftUI #CleanArchitecture #MobileArchitecture #SoftwareDesign #Scalability #ModularApps #TechLeadership #SwiftLang