From `Hello, World`to App Store Reviewin 12 Weeks.

class="token-comment">// Protocol-oriented approach
protocol DataFetchable {
  associatedtype Response: Decodable
  func fetch() async throws -> Response
}

struct UserService: DataFetchable {
  typealias Response = [User]
  
  func fetch() async throws -> [User] {
    let (data, _) = try await URLSession
      .shared.data(from: .usersEndpoint)
    return try JSONDecoder().decode(
      [User].self, from: data)
  }
}

class="token-comment">// MVVM + Combine
final class UserListViewModel: ObservableObject {
  @Published var users: [User] = []
  @Published var isLoading = false
  
  private let service: any DataFetchable
  private var cancellables = Set()
  
  init(service: some DataFetchable) {
    self.service = service
  }
  
  func loadUsers() {
    isLoading = true
    Task { @MainActor in
      users = try await service.fetch()
      isLoading = false
    }
  }
}

class="token-comment">// Production Core Data stack
final class PersistenceController {
  static let shared = PersistenceController()
  
  let container: NSPersistentCloudKitContainer
  
  var viewContext: NSManagedObjectContext {
    container.viewContext
  }
  
  func newBackgroundContext() 
    -> NSManagedObjectContext {
    let ctx = container.newBackgroundContext()
    ctx.mergePolicy = 
      NSMergeByPropertyObjectTrumpMergePolicy
    return ctx
  }
}

class="token-comment">// Custom map annotation
final class TransitAnnotation: NSObject, 
  MKAnnotation {
  dynamic var coordinate: CLLocationCoordinate2D
  let vehicleId: String
  let routeColor: UIColor
  
  init(vehicle: Vehicle) {
    coordinate = vehicle.location
    vehicleId = vehicle.id
    routeColor = vehicle.route.color
  }
}

class="token-comment">// Batch update without full reload
func updateAnnotations(_ vehicles: [Vehicle]) {
  mapView.removeAnnotations(staleAnnotations)
  mapView.addAnnotations(freshAnnotations)
}

class="token-comment">// WidgetKit timeline provider
struct TransitProvider: TimelineProvider {
  func getTimeline(
    in context: Context,
    completion: @escaping (Timeline) -> Void
  ) {
    Task {
      let arrivals = try await 
        TransitService.shared.nextArrivals()
      
      let entries = arrivals.map { arrival in
        TransitEntry(
          date: arrival.fetchedAt,
          nextBus: arrival
        )
      }
      completion(Timeline(
        entries: entries,
        policy: .atEnd
      ))
    }
  }
}

# Fastlane Matchfile + Deliverfile
# automated signing & submission

lane :release do
  ensure_git_status_clean
  
  increment_build_number(
    build_number: latest_testflight_build_number + 1
  )
  
  match(type: "appstore")
  
  run_tests(scheme: "CompileApp")
  
  build_app(
    scheme: "CompileApp",
    export_method: "app-store"
  )
  
  upload_to_app_store(
    submit_for_review: true,
    automatic_release: false
  )
end