Hands-On Design Patterns with Swift

Early view access in properties

The preceding example made it clear that we should not load views in the constructor. Now, consider the following generic code that helps us to write controllers with an asynchronous state:

enum State<T> {    case unknown, loading    case loaded(T)    case error(Error)}class StateController<T>: UIViewController {    var state: State<T> = .unknown {        didSet { updateState() }    }    private func updateState() {        switch state {        case .loading:           view.alpha = 0.0 // make it transparent while loading        case .loaded(_):           view.alpha = 1.0 // show it when loaded        default: break;        }    }}// In another view controllerlet controller = StateController<String>()controller.state = .loadingpresent(controller, animated: true, completion: nil)

This example ...