Question

A Java event logging (analytics) library has a method that takes an event name and then varargs list of Strings like this:

Analytics.event("my event name", "key1", "value1", "key2", "value2" ...)

I’ve collected my event parameters in to a Map like

Map("key1" -> "value1", "key2" -> "value2" ...)

Now there must be a way to flatten the Map to list where keys and values alternate and then feed it to the event method. I’ve had several guesses, like transforming the Map to list a List of Tuples, but calling .flatten on that says

No implicit view available from (java.lang.String, java.lang.String) => scala.collection.TraversableOnce[B]

What am I missing here?

Answer 1

You can use the : _* operator:

def event(name: String, values: String*) {/*...*/}

val params = Map("key1" -> "value1", "key2" -> "value2")
val paramsArr = params flatMap {case(k, v) => List(k, v)} toArray

event("name", paramsArr: _*)

Not sure whether this works with Java varargs as well (let us know!)