Rx에서 reactive base type 만들 때 자주 하는 실수

Correct.kt

    override fun connectDevice(userDeviceRef: UserDeviceRef, deviceAttributes: DeviceAttributes, nodeRef: PilsnerRef): Completable
            = Completable.fromRunnable {
        rwLock.write {
            devicePresences[userDeviceRef.deviceId] = Presence(userDeviceRef, deviceAttributes, nodeRef)
            userDevices.put(userDeviceRef.userId, userDeviceRef.deviceId)
        }
    }

    override fun getPresencesOfUser(userId: UserId): Single<List<Presence>>
            = Single.fromCallable {
        rwLock.read {
            val deviceIds = userDevices.get(userId)
            deviceIds.mapNotNull { devicePresences[it] }
        }
    }

Incorrect.kt

    override fun connectDevice(userDeviceRef: UserDeviceRef, deviceAttributes: DeviceAttributes, nodeRef: PilsnerRef): Completable
            = rwLock.write {
        devicePresences[userDeviceRef.deviceId] = Presence(userDeviceRef, deviceAttributes, nodeRef)
        userDevices.put(userDeviceRef.userId, userDeviceRef.deviceId)
    }.let { Completable.complete() }

    override fun getPresencesOfUser(userId: UserId): Single<List<Presence>>
            = rwLock.read {
        val deviceIds = userDevices.get(userId)
        deviceIds.mapNotNull { devicePresences[it] }
    }.let { Single.just(it) }