How can I save data in ReactiveX

Question

I'm new to ReactiveX and I have a question. How can I save data in ReactiveX. For example. I have this code.

last_price = market_data_service.get_last_price("IBM")
difference = previous_last_price - last_price 

For its correct work, I need to know the previous value of the price. How can I save the previous price in ReactiveX.

Answer 1

In RX methods returns Observable<T>. So in your case, above should be:

int previous_last_price = 10;
Single<Integer> market_data_service = Single.just(5);
Single<Integer> difference = market_data_service.map(last_price -> previous_last_price - last_price);