ios-uikit-architecture

# iOS - UIKit Architecture

Architectural patterns and best practices for UIKit-based iOS applications.

## Key Concepts

### MVVM Architecture

The Model-View-ViewModel pattern separates concerns:

- **Model**: Data and business logic
- **View**: UIViewController and UIView subclasses
- **ViewModel**: Presentation logic, transforms model data for display

```swift
// Model
struct User {
    let id: String
    let firstName: String
    let lastName: String
    let email: String
}

// ViewModel
class UserProfileViewModel {
    private let user: User

    var displayName: String {
        "\(user.firstName) \(user.lastName)"
    }

    var emailDisplay: String {
        user.email.lowercased()
    }

    init(user: User) {
        self.user = user
    }
}

// View
class UserProfileViewController: UIViewController {
    private let viewModel: UserProfileViewModel

    init(viewModel: UserProfileViewModel) {
        self.viewModel = viewModel
        super.init(nibName: nil, bundle: nil)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        nameLabel.text = viewModel.displayName
        emailLabel.text = viewModel.emailDisplay
    }
}
```

### Coordinator Pattern

Coordinators handle navigation flow, removing navigation logic from view controllers:

```swift
protocol Coordinator: AnyObject {
    var childCoordinators: [Coordinator] { get set }
    var navigationController: UINavigationController { get }
    func start()
}

class AppCoordinator: Coordinator {
    var childCoordinators: [Coordinator] = []
    var navigationController: UINavigationController

    init(navigationController: UINavigationController) {
        self.navigationController = navigationController
    }

    func start() {
        let vc = HomeViewController()
        vc.coordinator = self
        navigationController.pushViewController(vc, animated: false)
    }

    func showDetail(for item: Item) {
        let detailCoordinator = DetailCoordinator(
            navigationCon