Sample_of_rx_switch_map_the_actions.kt

private fun toShareAction(): Observable<ShareProgressState> {
    // 1. Generate BMP
    return getGenBmpObservable()
        // 2. Show dialog
        .switchMap { _ -> 
            getDialogSingle()
                .toObservable()
        }
        // 3. Share
        .switchMap { dialogPayload -> 
            if (dialogPayload.result == RESULT_OK) {
                // If the user clicks OK, share to FB.
                getShareToFacebookObservable(dialogPayload.data)
            } else {
                // The EMPTY observable calls observer's onComplete()
                // to indicate the stream is over.
                Observable.empty()
            }
        }
}

/**
 * Returns a CANCEL action.
 */
private fun toCancelAction(): Observable<ShareProgressState> {
    return Observable.just(ShareProgressState(justStop = true))
}