我如何在Scala中获取类列表的元素的字符串

Question

I have a List of a class where the class is defined like:

case class Role (role_id, elem2, elem3)

well sort of...

so if I have a List of those as roles: List[Role]

how can I get a string of the role_id's so that if my list had 4 Roles in it my string might look like "3 6 8 9" ?

or better still how can i add some string to it so i can get "3, 6, 8, 9" ?

im having to craft some sql and want set based operations instead of looping. I feel i should flatten or something but i cant think

Thank you Martin

Answer 1

Try something like this:

scala> case class Role(role_id: Int, elem2: String, elem3: String)
defined class Role

scala> val l = List(Role(1, "", ""), Role(2, "", ""), Role(3, "", ""))
l: List[Role] = List(Role(1,,), Role(2,,), Role(3,,))

scala> l.map({ case Role(id, _, _) => id }).mkString(", ")
res2: String = 1, 2, 3