CODESAMPLE

N-tier - Swift

N-tier Swift

The N-tier pattern organizes an application into distinct layers, each with a specific responsibility. This promotes separation of concerns, making the application more maintainable, testable, and scalable. A typical N-tier architecture includes a presentation tier (UI), a business logic tier, and a data access tier.

This Swift example demonstrates a simplified 3-tier architecture for managing user data. The User struct represents the data model. UserService encapsulates the business logic for user operations (e.g., fetching, creating). UserRepository handles the data access, simulating a database interaction. The use of protocols for UserRepository allows for easy dependency injection and testing with mock data sources. This structure aligns with Swift’s emphasis on clear separation of concerns and testability through protocols and structs.

// Model
struct User {
    let id: Int
    let name: String
    let email: String
}

// Data Access Tier (Repository)
protocol UserRepository {
    func getUser(byId id: Int) -> User?
    func saveUser(user: User)
}

class DefaultUserRepository: UserRepository {
    private var users: [User] = [
        User(id: 1, name: "Alice", email: "alice@example.com"),
        User(id: 2, name: "Bob", email: "bob@example.com")
    ]

    func getUser(byId id: Int) -> User? {
        return users.first { $0.id == id }
    }

    func saveUser(user: User) {
        users.append(user)
    }
}

// Business Logic Tier (Service)
class UserService {
    private let userRepository: UserRepository

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

    func getUserDetails(userId: Int) -> User? {
        return userRepository.getUser(byId: userId)
    }

    func createUser(name: String, email: String) -> User {
        let newUser = User(id: Int.random(in: 1000..=9999), name: name, email: email)
        userRepository.saveUser(user: newUser)
        return newUser
    }
}

// Presentation Tier (Example Usage)
let userRepository = DefaultUserRepository()
let userService = UserService(userRepository: userRepository)

if let alice = userService.getUserDetails(userId: 1) {
    print("User Name: \(alice.name), Email: \(alice.email)")
}

let newuser = userService.createUser(name: "Charlie", email: "charlie@example.com")
print("Created new user: \(newuser.name) with ID: \(newuser.id)")