//in viewModel
let logical = Variable<String>("")
let presentation = Variable<String>("")

func keyPressed(keyID: Int) {

    //do
    logical.value = "what?"
    presentation.value = "what?"
}

//in controller
func youWantToDo() {

    logical.asObservable().subscribe(onNext: <#T##((String) -> Void)?##((String) -> Void)?##(String) -> Void#>, onError: <#T##((Error) -> Void)?##((Error) -> Void)?##(Error) -> Void#>, onCompleted: <#T##(() -> Void)?##(() -> Void)?##() -> Void#>, onDisposed: <#T##(() -> Void)?##(() -> Void)?##() -> Void#>)

    presentation.asObservable().bind(to: <#T##ObserverType#>)
}