ObservableViewController - functional reactive View Lifecycle handling with Combine

ObservableViewController.swift

import Combine
import UIKit

/// View controller, that publishes events for it's `view`'s lifecycle,
/// and allows type safe access to it's main `UIView`.
class ObservableViewController<V: UIView>: UIViewController {

    typealias LifecycleEvent = (view: V, animated: Bool)

    /// Broadcasts event after the controller's view is loaded, e.g. `viewDidLoad()`.
    var onViewDidLoad: AnyPublisher<Void, Never> {
        onViewDidLoadPublisher.eraseToAnyPublisher()
    }

    /// Broadcasts events when the controller's view was added to a view hierarchy, e.g. `viewDidAppear(...)`.
    var onDidAppear: AnyPublisher<LifecycleEvent, Never> {
        onDidAppearPublisher.eraseToAnyPublisher()
    }

    private lazy var onViewDidLoadPublisher = PassthroughSubject<Void, Never>()
    private lazy var onDidAppearPublisher = PassthroughSubject<LifecycleEvent, Never>()

    /// Type safe access to the controller's main `UIView`.
    lazy var contentView: V = V()

    override func loadView() {
        view = contentView
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        onViewDidLoadPublisher.send()
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        onDidAppearPublisher.send((contentView, animated))
    }
}