LanguageListCoordinator.swift

/// Type that defines possible coordination results of the `LanguageListCoordinator`.
///
/// - language: Language was choosen.
/// - cancel: Cancel button was tapped.
enum LanguageListCoordinationResult {
    case language(String)
    case cancel
}

class LanguageListCoordinator: BaseCoordinator<LanguageListCoordinationResult> {

    private let rootViewController: UIViewController

    init(rootViewController: UIViewController) {
        self.rootViewController = rootViewController
    }

    override func start() -> Observable<CoordinationResult> {
        // Initialize a View Controller from the storyboard and put it into the UINavigationController stack
        let viewController = LanguageListViewController.initFromStoryboard(name: "Main")
        let navigationController = UINavigationController(rootViewController: viewController)

        // Initialize a View Model and inject it into the View Controller
        let viewModel = LanguageListViewModel()
        viewController.viewModel = viewModel

        // Map the outputs of the View Model to the LanguageListCoordinationResult type
        let cancel = viewModel.didCancel.map { _ in CoordinationResult.cancel }
        let language = viewModel.didSelectLanguage.map { CoordinationResult.language($0) }

        // Present View Controller onto the provided rootViewController
        rootViewController.present(navigationController, animated: true)

        // Merge the mapped outputs of the view model, taking only the first emitted event and dismissing the View Controller on that event
        return Observable.merge(cancel, language)
            .take(1)
            .do(onNext: { [weak self] _ in self?.rootViewController.dismiss(animated: true) })
    }
}