WWDC.2019.Combine.kvo.swift

@available(iOS 13.0, *)
func exampleCombineKVO () {
    let article = Article(title: "Test", body: "Lorum ipsum")
    // For a KeyPath 101, see https://www.swiftbysundell.com/posts/the-power-of-key-paths-in-swift
    let keypath: ReferenceWritableKeyPath<Article,String> = \.title
    
    // The new Combine stuff:
    let sink = Subscribers.Assign(object: article, keyPath: keypath)

    let source = Publishers.Future<String, Never> { subscriber in
        DispatchQueue.main.async {
            subscriber(.success("42"))
        }
    }
    
    source.subscribe(sink)
}