flatMapLatest

flatMapLatestで、最新のストリームだけをflatMap出来る

Scan

前の値と流れてくる値にアクセスが出来て

Observable.of(1..<10)
  .scan(nil) { preventalue, newValue in
     preventValue + neValue
  }
  .subscribeNext { print("\\($0") }

extension

func combinePrevious(_ initial: Element) -> Observable<(Element, Element)> {
   return scan((initial, initial)) { previousValues, newValue in
      return (previousValues.1, newValue
   }
}

//how to using
observable.of(1..<2)
  .combinePrevious(nil)
  .subescribeNext { print("\\($0.1 + $0.2))")  }

takeUntil