`doAfterSubscribe` operator?

So I came from this StackOverFlow thread RxJava - .doAfterSubscribe()?. So that combination of mergeWith()/startWith() and doOnComplete works really fine but I think it’s a bit too creative to come up with by myself. I think lots of us want this approche because we are trying/experimenting for this architecture by Jake Wharton in the talk of Devoxx here: The State of Managing State with RxJava . So I wonder why don’t we have a build-in operator that can do this sort of work after your subscriber set up. So it’s like a part of Observable can survive out side of the stream as a Subject. Thanks!

[akarnokd]

Operators have to be common enough, in-sequence and well defined to be considered including in RxJava proper. Sometimes, the context isn’t well defined or the operator is supposed to support a small set of developers’ thinking about solving a problem that can be solved through existing operators and composition (often requiring changing the viewpoint on the original problem as well).

RxJava is quite extendable through compose and you can write your own operator that intervenes in the lifecycle of a flow. For added convenience, you can consider using Kotlin where its extension methods even help you to make that custom operator appear to be an instance method on the reactive types of RxJava.

[akarnokd]

Write an ObservableTransformer and call compose with it.