let disposeBag = DisposeBag()
let first = BehaviorSubject(value: "👦🏻")
let second = BehaviorSubject(value: "🅰️")
let variable = Variable(first)
variable.asObservable()
.flatMapLatest { $0 }
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
first.onNext("🐱")
variable.value = second
second.onNext("🅱️")
first.onNext("🐶")