I’m new to Scala, and this problem frustrates me. How can I get all headers from request? val route = { path(“lol”) { //get httpHeaders complete(HttpResponse()) } } Answer You have at least two options here: a) Using extractRequest directive: val route = { path(“example”) { extractRequest { request => request.headers // Returns `Seq[HttpHeader]`; do … Read more
I have an Akka Streams Source which I want to split into two sources according to a predicate. E.g. having a source (types are simplified intentionally): val source: Source[Either[Throwable, String], NotUsed] = ??? And two methods: def handleSuccess(source: Source[String, NotUsed]): Future[Unit] = ??? def handleFailure(source: Source[Throwable, NotUsed]): Future[Unit] = ??? I would like to be … Read more
I have a set of case classes like this abstract class Shape case class Rectangle(width: Int, height: Int) extends Shape case class Location(x: Int, y: Int, shape: Shape) extends Shape case class Circle(radius: Int) extends Shape case class Group(shape: Shape*) extends Shape where basically Group is an array of shapes. I need to define a … Read more
Long time java programmer slowly learning scala (loving it by the way), and I think my mind is still wrapping itself around the concept of writing things functionally. Right now I’m attempting to write a simple visualizer for some moving 2d textures. The imperative approach is simple enough, and I’m sure most of you will … Read more
I can define a variable (by var) that is immutable: var x = scala.collection.immutable.Set(“aaaaaa”,”bbbbbb”) println(x.isInstanceOf[scala.collection.immutable.Set[String]]) x += “cccc” println(x.isInstanceOf[scala.collection.immutable.Set[String]]) This results in: true true += method is not a member of scala.collection.immutable.Set, so what is happening? Answer The compiler looks for x.+= …, and if it can’t find it, then it tries to transform the … Read more
Does anyone have advice on using cassandra with scala? There is no native scala-cassandra client supporting cassandra version 8.0+, so I have to use hector, and it seems to work OK but not to be concise. Do you have any attempts, recommendations or any wrapper code,.. etc for hector ? Answer The official Scala driver … Read more
Is there a shorter/better way to do the following : mySeq.map { elmt => // do stuff } if (mySeq.isEmpty) { // some other stuff } Ps : I’m using PlayFramework and this is meant to be used in templates, so if there are any “helpers” there I missed, I would be glad to discover … Read more
In Play 1 it was simply: @Every(value = “1h”) public class WebsiteStatusReporter extends Job { @Override public void doJob() throws Exception { // do something } } What is the equivalent for Play 2.1? I know that Play uses akka and I found this code sample: import play.api.libs.concurrent.Execution.Implicits._ Akka.system.scheduler.schedule(0.seconds, 30.minutes, testActor, “tick”) But being a … Read more
In my Scala program, I am receiving some JSON. One of the fields is an optional Boolean. If the field is missing, or if its value is false, I would like to return None. If its value is true, I would like to return Some(true). SInce this is equivalent to converting Some(false) into None, I … Read more
How do I merge 2 lists in such a way that the resulting list contains the elements of 2 lists in alternating fashion in Scala. Input: val list1 = List(“Mary”, “a”, “lamb”) val list2 = List(“had”, “little”) Output: List(“Mary”, “had”, “a”, “little”, “lamb”) Answer What you’re looking for is usually called “intersperse” or “intercalate” and … Read more
