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’m learning Scala and there is a thing that I can’t find out about the language: Some time ago I was very comfortable programming in Lisaac, and in Lisaac I could write a class PERSON with a slot list:ARRAY[SELF], which was equivalent to have list:ARRAY[PERSON], since SELF is the type of the object where that … 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
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
I’m searching for a possiblity in scala to call a function and get an Option as result which is “None” iff either an Exception is raised when calling the method or the method return null. Otherwise the Option should have the value of the result. I know that Try can be used for the first … Read more
