ios – How do I flatMap two singles?

I’ve an observable that appears like this:

func getParameters() -> Single<[ParameterModel]?> {
    do {
        loading.settle for(allParameters.isEmpty)
        return strive parameterService.getParameters()
            .do(onSuccess: { [weak self] parameters in
                self?.loading.settle for(false)
                self?.content material.settle for(parameters?.compactMap { $0 }
                                                .compactMap { TechnicianParameterTableViewCellViewModel(parameter: $0) } ?? [])
            })
    } catch { return Single.error(error) }
}

The vital half is the place it compactMaps right into a cell. This works as anticipated. However I even have one other observable that appears like this:

func getSingleOrDoubleDoor() -> Single<SingleOrDoubleDoor?> { //SingleOrDoubleDoor is an enum
    do {
        return strive parameterService.getSingleOrDoubleDoor()
    } catch {
        return Single.error(error)
    }
}

Now, I wish to kind of merge getSingleOrDoubleDoor() into getParameters() in order that I can entry the values of each observables in onSuccess. I need to use the outcome kind of like this:

.compactMap { TechnicianParameterTableViewCellViewModel(parameter: $0, isSingleOrDouble: $1) } ?? [])

Not being an knowledgeable on Rx I nonetheless assume that that is executed utilizing .flatMap{}. Type of like:

...return strive parameterService.getParameters().flatMap { _ in getSingleOrDoubleDoor() }...

However this provides me an error:

Can’t convert worth of kind ‘([ParameterModel]?) -> Single<SingleOrDoubleDoor?>’ (aka ‘(Non-compulsory<Array>) -> PrimitiveSequence<SingleTrait, Non-compulsory>’) to anticipated argument kind ‘([ParameterModel]?) throws -> PrimitiveSequence<SingleTrait, [ParameterModel]?>’

Tried altering the return expression nevertheless it nonetheless would not take. Unsure easy methods to make this occur.