Scala Future with Option() -

i'm creating 3 actor tasks using future, , trying collect 3 when finished. current code following:

implicit val timeout = timeout(5.seconds)   val result1 = actor1 ? dataforactor(data)   val result2 = actor2 ? dataforactor(data)   val result3 = actor3 ? dataforactor(data)   val answer = {     <- result1.mapto[list[resultdata]]     b <- result2.mapto[list[resultdata]]     c <- result3.mapto[list[resultdata]]   } yield (a ++ b ++ c).sorted   answer oncomplete {     case success(resultdata) =>       log.debug("all actors completed succesffully")       successactor ! successdata(resultdata.take(2))     case failure(resultdata) =>       log.info("actors failed")   } 

each of actors (actor1, actor2, actor3) manipulates data , returns either none or option(list(resultdata)), shown in following code:

val resultdata = if(data.size == 0) none else {   data.map {     ...     try {       ... //manipulation on resultdata       option(resultdata)     }     catch {       case e: exception => none     }   }.flatten } 

the statement concatenates lists each actor, , produces long list(resultdata).

i want in case 1 actor returns none, it's result in statement not add concatenation, i.e. list().

an example:

if get: result1 = list(1, 2, 3), result2 = none, result3 = list(4, 5),

i want: resultdata = list(1, 2, 3, 4, 5)

you replace none nil before mapto way:

result1.map{   case none => nil   case x => x }.mapto[list[resultdata]] 

note should avoid mapto generic type list:

future("x" :: nil).mapto[list[int]] // res0: scala.concurrent.future[list[int]]  future("x" :: nil).mapto[list[int]] foreach { _.map( _ + 1 ) } // java.lang.classcastexception: java.lang.string cannot cast java.lang.integer 

because of type erasure mapto can't prove have list of int, not list of other type. you'll same problem case l: list[int] in receive method of actor.

you should create special class messages this:

sealed trait resultlist { def data: list[resultdata] } case class notemptyresult(data: list[resultdata]) extends resultlist  case object emptyresult extends resultlist { def data: list[resultdata] = nil }  result1.mapto[resultlist]