CODEWITHSUNDEEP
reactive-programmingrx-java
EstusFlask
EstusFlask

Reputation: 53

Can I have an Observable that emits values to be used by another Observable?

I am new to rx-java and may not be using it correctly, but this is what I am trying to do:

I have an Observable<String> that stores some data in an external database and emits a String which is the path or key to the data that was stored.

I have a second Observable<Boolean> that takes a String and puts it on a queue and emits whether that operation was successful.

I want to 'chain' these two Observables such that when the Observable<String> emits a path, the Observable<Boolean> puts it on a queue and returns whether it was successful. I want to end up with a single Observable that performs both of these operations.

I haven't been able to find any API methods that let me do what I want so I am starting to think that I am not using rx-java properly. It seems like I need to take my Observable<String> and call .map() to turn it into an Observable<Boolean>, but by doing this I am not able to use my original Observable<Boolean> other than by just running it as a blocking method inside of map(), but it may as well just be a Callable at that point.

edit: seems like I should probably be using Singles rather than Observables as my Observables only need to emit one value before completing.

Upvotes: 2

Views: 618

Answers (1)

Dave Moten
Dave Moten

Reputation: 12087

Looks like flatMap is what you are looking for.

So you have:

Observable<String> data;

and method 

Observable<Boolean> putOnQueue(String path);

Then you could do:

Observable<Boolean> result = data.flatMap(path -> putOnQueue(path));

Upvotes: 1

Related Questions