I am dealing with a problem where the last `x` val...

# rx

[nhaarman]

I am dealing with a problem where the last x values emitted by bar are stored in some state, and foo emits y values for each value bar emits based on this state. My solution was to call emitter.onNext y times, and store the state inside the create block.
Now I realize that a concatMap like this does the same:

// receiver is `bar`
fun Observable<Int>.foo() : Observable<Int> {
  var state = emptyState()
  
  return concatMap { value ->
     val values : List<Int> = calculateValues(value, state)
     state = state.updateWith(value)
     Observable.fromIterable(value)
  }
}

This of course keeps a single stream including error and terminal messages 🙂