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I have a list of string ids representing DB records. I'd like to load them from the DB asynchronously, then upload each record to a remote server asynchronously, then when all are done uploading, make a record of the ids of the records that were uploaded. Since I'm on Scala 2.9.2, I'm using Twitter's core-util Future implementation, but it should work exactly like the 2.10 futures in terms of Monadic transformations. The general concept is this: def fetch(id: String): Future[Option[Record]] def upload(record: Record): Future[String] def notifyUploaded(ids: Seq[String]): Unit val ids: Seq[String] = .... I'm trying to do this via a for comprehension but the fact that fetch returns a Future of Option makes it obscure and the code doesn't compile: for { id <- ids maybeRecord <- fetch(id) record <- maybeRecord uploadedId <- upload(record) } yield uploadedId Compiling this results in the following error: scala: type mismatch; found : com.twitter.util.Future[String] required: Option[?] uploadedId <- upload(record) ^ What am I missing? why does the compiler expect uploadedId to be an Option? is there any pretty way I could work around this?

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