I have a sequence of Users in a collection
val users: Seq[User]
And I want to pass it into the Queue.enqueue method that takes:
def enqueue(elems : A*)
I can foreach on my collection but I am sure there is a way to convert it right?
Also, what is A* called again?
A* is a varargs type. To pass a collection to such a function, you can use the special vararg-expansion syntax, like this:
queue.enqueue(seq: _*) // If queue is of type Queue[User].
You can use this notation only if your collection is a Seq, or if it can be implicitly converted to a Seq.
As soon as A is a type parameter and is compatible (as for type constraints/variance) with User:
enqueue(users: _*)
If the queue is mutable, you can use enqueue as pointed out by other answers
or use ++=
scala> val mQueue = scala.collection.mutable.Queue[Int](1, 2, 3, 4, 5)
mQueue: scala.collection.mutable.Queue[Int] = Queue(1, 2, 3, 4, 5)
scala> val aSeq = Seq[Int](6, 7, 8, 9, 10)
aSeq: Seq[Int] = List(6, 7, 8, 9, 10)
scala> mQueue ++= aSeq
res26: mQueue.type = Queue(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
If the queue is immutable, you have to use enqueue as following:
scala> val imQueue = scala.collection.immutable.Queue[Int](1, 2, 3, 4, 5)
imQueue: scala.collection.immutable.Queue[Int] = Queue(1, 2, 3, 4, 5)
scala> imQueue.enqueue(aSeq.toList)
res32: scala.collection.immutable.Queue[Int] = Queue(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
In case of immutable, as the name suggests, imQueue is not updated, instead
another immutable queue is returned.
scala> imQueue
res33: scala.collection.immutable.Queue[Int] = Queue(1, 2, 3, 4, 5) // still original values
