Single::flatMapCompletable in RxSwift

flatMapCompletable.swift

extension PrimitiveSequenceType where Self: ObservableConvertibleType, Self.TraitType == SingleTrait {
    
    func flatMapCompletable(_ selector: @escaping (E) -> Completable) -> Completable {
        return self
            .asObservable()
            .flatMap { e -> Observable<Never> in
                selector(e).asObservable()
            }
            .asCompletable()
    }
    
}