ChainApi2.kt

fun zipApi1AndApi2(): Observable<Pair<Media, okhttp3.Response>> {
    return Api.api1().flatMap { response ->
        if (response.isSuccessful) {
            var uploadUrl = response.headers().get(ApiUtils.Header.LOCATION)
            uploadUrl?.let {url ->
                Observable.zip(
                    Observable.just(response.body()),
                    Api.api2(url)
                ) { t1, t2 -> Pair(t1, t2) }
            } ?: run {
                throw Exceptions.propagate(NullPointerException("Media upload URL is empty"))
            }
        } else
            Observable.error(ApiRequestException(response))
    }
}