How can I add a class to Scala Set - scala

Question

I would like to passing a parameter via String and construct a Set of class objects, like this:
def getTypes(value: String) : Set[Class[Base]] = {
var set = Set[Class[Base]]()
var input = value.split(",")
if(input.contains("XXX"))
set ++ Class[xxx]
if(input.contains("YYY"))
set ++ Class[yyy]
if(input.contains("ZZZ"))
set ++ Class[zzz]
set
}
Then looping the set and use class.newInstance() to create the actual object to do something later. The able code can compile, but when it run, it complaint that
Error:(32, 16) object java.lang.Class is not a value
set ++ Class[xxx]
Any clue about about that?

Answer 1

There are two problems in your snippet. One, as aravindKrishna pointed, is you're trying to get Class literals improperly.
The other one is, you're treating your immutable Set like you would a mutable one. Remember you can't mutate the object itself - every operation returns a new one - so you should either reassign the variable every time (and using vars is discouraged for functional code), or use recursion, or construct the entire set in one go.
Here's an example of how to construct the set in one go:
def getTypes(value: String): Set[Class[_ <: Base]] = {
val mapping = Map(
"XXX", classOf[xxx],
"YYY", classOf[yyy],
"ZZZ", classOf[zzz])
val input = value.split(",").toSet
mapping.collect {
case (k, v) if input contains k => v
}.toSet
}
Or, translating your original code snippet more literally,
def getTypes(value: String): Set[Class[_ <: Base]] = {
val input = value.split(",").toSet
Set[Class[_ <: Base]]() ++
input.find("XXX" ==).map(_ => classOf[xxx]) ++
input.find("YYY" ==).map(_ => classOf[yyy]) ++
input.find("ZZZ" ==).map(_ => classOf[zzz])
}