You have two tables in Room(Rx), let say A & B...

# android

[pollux-]

You have two tables in Room(Rx), let say A & B. You have to check in table A, if the value returned is valid then check table B and return the result. Else return error to the user. How can this be done using single stream in Rx. Any suggestions?

[Guillermo Alcantara]

Not sure I understand the question. Could you tableASingle.flatMap { tableBSingle } ?

[psh]

I think there’s a small step in between,

queryTableA.flatMap {
    if (invalid) {
        Single.error(...)
    } else {
        queryTableB
    }
}

[pollux-]

If inside the flatMap .. there is no way to avoid this ?

[pollux-]

IMG_20200728_124750.jpg

[pollux-]

@Guillermo Alcantara

[Guillermo Alcantara]

avoid what?

[pollux-]

There is an IF check inside the flatMap(). Can we avoid that . That's look ugly to me 😂

[Guillermo Alcantara]

well you could map the first single and throw an exception if invalid, but that's worse imo

[Guillermo Alcantara]

if you are into that, you could create an extension filterWithError that does that and can be reused for other streams. Where if predicate is true passes it downstream, otherwise errs.