RxJava 예제 코드

class UserRepository(val userApi: UserApi) {

    var cachedUsers = emptyList<User>()

    fun getUsers(): Observable<List<User>> {
        if (cachedUsers.isEmpty()) {
            //Returning users from API
            return userApi.getUsers()
                    .doOnNext { cachedUsers = it }
        } else {
            //Returning cached users first, and then API users
            return Observable.just(cachedUsers)
                    .mergeWith(userApi.getUsers())
                    .doOnNext { cachedUsers = it }
        }
    }
}