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

DomainEvents.swift

protocol ListingService: class {
    var events: Observable<ListingServiceEvent> { get }
    func filteredEvents(listing: Listing) -> Observable<ListingServiceEvent>
    
    func create(params: ListingServiceCreateParams,
                completion: ((Result<Listing, ListingServiceCreateError>) -> ())?)
    func update(listing: Listing,
                params: ListingServiceUpdateParams,
                completion: ((Result<Listing, ListingServiceUpdateError>) -> ())?)
    func delete(listing: Listing,
                completion: ((Result<Listing, ListingServiceDeleteError>) -> ())?)
}

enum ListingServiceEvent {
    case create(listing: Listing)
    case update(listing: Listing)
    case delete(listing: Listing)
}