Example of implementation of Domain Events in Swift. The snippet illustrates Domain Events in a Service with RxSwift

DomainEvents-2.swift

import RxSwift

class LocalListingService: ListingService {
    var events: Observable<ListingServiceEvent> {
        return eventsPublishSubject.asObservable()
    }
    private let eventsPublishSubject: PublishSubject<ListingServiceEvent>

    // ...

    func create(params: ListingServiceCreateParams,
                completion: ((Result<Listing, ListingServiceCreateError>) -> ())?) {
        let listing = Listing(id: String.makeRandom(length: 5),
                              title: params.title,
                              price: params.price)
        let result = Result<Listing, ListingServiceCreateError>.success(data: listing)
        let deadline: DispatchTime = .now() + .milliseconds(50)
        DispatchQueue.main.asyncAfter(deadline: deadline) { [weak self] in
            defer { completion?(result) }
            self?.eventsPublishSubject.onNext(ListingServiceEvent.create(listing: listing))
        }
    }

    // ...
}