RxSwiftのflatMapFirstで `isLoading` 的なフラグ管理相当のことができることの確認 #CodePiece

CodePiece.swift

let trigger = PublishSubject<Void>()

func fetch() -> Single<String> {
    return Single.create { observer in
        print("🛫")
        DispatchQueue.global().async {
            usleep(2_500_000)
            print("🛬")
            observer(.success("レスポンス"))
        }
        return Disposables.create()
    }
}

trigger
    .debug("▶️")
    .flatMapFirst { fetch() }
    .subscribe(onNext: { print("👀", $0) })

trigger.onNext(())
sleep(1)
trigger.onNext(())
sleep(1)
trigger.onNext(())
sleep(1)
trigger.onNext(())
sleep(1)
trigger.onNext(())

/*
 2017-12-05 12:34:11.546: ▶️ -> subscribed
 2017-12-05 12:34:11.548: ▶️ -> Event next(())
 🛫
 2017-12-05 12:34:12.551: ▶️ -> Event next(())
 2017-12-05 12:34:13.554: ▶️ -> Event next(())
 🛬
 👀 レスポンス
 2017-12-05 12:34:14.557: ▶️ -> Event next(())
 🛫
 2017-12-05 12:34:15.560: ▶️ -> Event next(())
 🛬
 👀 レスポンス
 */