iOS RxSwift - how to use Amb Operator?

Question

I'm looking for example of Amb() operator for RxSwift.

I have two observables - started and stopped and I want to create code which would execute if one of them emits, while ignoring emissions from the other one.

let started = viewModel.networkAPI.filter { result in
            switch result {
            case .success:
                return true
            case .failure:
                return false
            }
        }

    let stopped = viewModel.networkAPI.filter { result in
        switch result {
        case .success:
            return true
        case .failure:
            return false
        }
    }

I tried:

    Observable<Bool>.amb([started, stopped])
//error - Ambiguous reference to member 'amb'
//Found this candidate (RxSwift.ObservableType)
//Found this candidate (RxSwift.ObservableType)

and:

 started.amb(stopped)
//error - Generic parameter 'O2' could not be inferred

How do I properly use RxSwift AMB operator to pick one of two observables to emit a value first?

Answer 1

The problem isn't in the code you posted. My guess is that your Result type is generic and the started and stopped observables are filtering off of different types of Result. In essence, started and stopped have different types and therefore, amb won't work with them.

You can test this by doing let foo = [started, stopped] and then testing the type of foo . You will probably get the error:

Heterogeneous collection literal could only be inferred to '[Any]'; add explicit type annotation if this is intentional

//convert both to the same emission type,
//then apply .amb after one of them

let stoppedBoolType = stopped.map { _ -> Bool in
    return false
}
started.map{ _ -> Bool in
    return true
    }.amb(stoppedBoolType)