Multiple for comprehensions within a map in Scala - scala

Question

Here is the function,
def checkSupport(request: checkSupportRequest): Future[checkSupportResponse] = {
val lookupClient = Thrift.newIface[lookupClient[Future]](/*some initializers*/)
val req = lookupIPRequest(request.getIps, /*Unimportant variables*/)
var result = new checkSupportResponse()
lookupClient.performLookup(req).map { resp =>
// Returns a map of IP to Country Code (String:String)
val ip_cc_map = for {
(ip, lxn) <- resp.found
sr <- lxn.simpleResult
cc <- sr.countryCode
} yield (ip, cc)
// Returns a map of IP to Boolean (String:Boolean)
val not_found_map = for {
(ip) <- resp.notFound
} yield (ip, false)
val op_supp_temp_map = ip_cc_map.map {
case (ip, cc) => someLookup(cc) //This returns a boolean value
}
val op_supp_map = op_supp_temp_map.toList //List of Booleans
val ips_found = ip_cc_map.map { // Intended to become a list of IPs
case (ip, cc) => ip
}
val final_op_supp_map = ips_found zip op_supp_map // Converted to Map (String:Boolean)
final_map = final_op_supp_map ++ not_found_map
result.set_supported(final_result.toList.toMap.mapValues(Boolean.box))
}
Future.value(result)
}
The performLookup is a futurized call. Is it kosher to do things as above i.e. take the output of the futurized call and map it. Perform two back-to-back for comprehensions on it to obtain the necessary maps and then subsequently in the same for, combine the two results and return the same. For some reason, this compiles but when I'm trying to unit-test it, it appears as if the performLookup never ran. Any help would be appreciated.
Also I am in my unit-test doing an Await.result() on the checkSupport() call.

Answer 1

I'm assuming that by Future.value(result) you actually mean Future.successful(result).
The result variable inside the closure is different from the result variable outside of it, so you're never actually modifying the result variable that you're declaring at the beginning of your function. So this is why it looks like your Future never ran.
As a side-note, even if you mutate the state of result, you don't need to declare it as var, val is good here (var would only be necessary if you were reassigning it by doing result = ...).
So you can modify your function like this:
def checkSupport(request: checkSupportRequest): Future[checkSupportResponse] = {
// declare lookupClient and req as before, but not res
lookupClient.performLookup(req).map { resp =>
// do all your processing like before
val result = new checkSupportResponse()
result.setOperator_supported(final_result.toList.toMap.mapValues(Boolean.box))
// We want "result" to be the result of the computation
result
}
}