Calling multiple web services - scala

Question

I'm using Play 2.5 with Scala, I created a class that will call multiple times external web services.
External web services are called on some condition and get a simple response of ok or nok. If it is ok then I should update internal objects status and if nok I do nothing for now.
Here is my class, it takes a list of list of String as paramters and return a Future list of object to be handled in the controller.
def callWSAndGetResponse(listOfList: List[List[String]]): Future[List[MyObject]] = {
val res = listOfList map { listOfIds =>
listOfIds map { id =>
val foundObj = allMyObject.find(obj => obj.id == id)
if(foundObj.isDefined) {
foundObj.get.urls map { url =>
val futureReponse: Future[WSResponse] = ws.url(url).get()
futureResponse map { response =>
(response.json \ "response").as[String]
}
}
}
}
}
// if responses are ok create a list of MyObject to return for example.
}
val res is of type list of list but I would like it to be just a simple list of response.
1) How to simplify and correct my code in order to get just a list of response, for later check if ok or not ?
2) How to check if responses are ok or have failed ?

Answer 1

It looks like you want this block to return a List[Future[Json]], from then you can use "List[Future] to Future[List] disregarding failed futures" or similar.
To do this you should use map and flatMap (rather than isDefined/get):
val res = listOfList map {
_.map { id =>
allMyObject
.find(obj => obj.id == id)
.map {
_.flatMap {url =>
val futureReponse: Future[WSResponse] = ws.url(url).get()
futureResponse map { response =>
(response.json \ "response").as[String]
}
}
}
}
}
if blocks assign to AnyVal rather than to a specific type (which will cause you issues here):
scala> if (true) 23
23: AnyVal
scala> if (false) 23
(): AnyVal
Using map keeps you in the Option monad:
scala> (None: Option[Int]).map(_ * 2)
None: Option[Int]