Swift Combine demo with RxSwift commenting

swiftcombine.swift

import Foundation
import Combine

// register the observable name
extension Notification.Name {
    static let DemoObservable = Notification.Name("DemoObservable")
}

// define the observable value type
struct DemoValue {
    let value: String
}

// create the observable
let observable = NotificationCenter.Publisher(center: .default, name: .DemoObservable, object: nil).map {
    (notification) -> String in
        return (notification.object as? DemoValue)?.value ?? ""
}

// define a handler for the subscription
class DemoHandler {
    var value: String = "foo"
}

// instantiate the handler
let handler = DemoHandler()
print("Pre-event: \(handler.value)")

// create a subscriber
let subscriber = Subscribers.Assign(object: handler, keyPath: \.value)

// subsubscribe to the observable
observable.subscribe(subscriber)

// publish an event
NotificationCenter.default.post(name: .DemoObservable, object: DemoValue(value: "bar"))

// value is changed post-event 
print("Post-event: \(handler.value)")