In RxJava, how to pass a variable along when chaining observables?

Another possibility is to map the result of op1 to a org.apache.commons.lang3.tuple.Pair that contains the variable and pass that along:

Observable
   .from(modifications)
   .flatmap( (data1) -> {
       return op1(data1).map( obj -> { return Pair.of(data1,obj); });
   })
   ...
   .flatmap( (dataPair) -> { 
       // data1 is dataPair.getLeft()
       return op2(dataPair.getRight());
   })

It works but it feels a bit uncomfortable to have variables hidden inside a Pair/Triple/... and it gets very verbose if you use the Java 6 notation.

I wonder if there is a better solution, maybe some RxJava operator could help?

The advice I got from the Couchbase forum is to use nested observables:

Observable
    .from(modifications)
    .flatmap( (data1) -> { 
        return op1(data1)
            ...
            .flatmap( (data2) -> { 
                // I can access data1 here
                return op2(data2);
            })
        });

EDIT: I'll mark this as the accepted answer as it seems to be the most recommended. If your processing is too complex to nest everything you can also check the solution with function calls.