FlatMap.swift

// Reference: [Transforming_Operators.xcplaygroundpage](https://github.com/ReactiveX/RxSwift/blob/master/Rx.playground/Pages/Transforming_Operators.xcplaygroundpage/Contents.swift)
let disposeBag = DisposeBag()

struct Player {
    var score: Variable<Int>
}

let 👦🏻 = Player(score: Variable(80))
let player = Variable(👦🏻)
player.asObservable()
    .flatMap { $0.score.asObservable() }
    .subscribe(onNext: { print("score: \($0)") }) //score: 80
    .disposed(by: disposeBag)