Scala append Seq in with a string in a List Map or Foreach

Question

I'm looking to append a val adminEmailSeq = Seq.empty[String] from a List of object attribute.

My List[User] called 'admins' and I'm trying to do this, but it doesn't work:

admins.foreach(
    admin => {
        adminEmailSeq :+ admin.email
    }
)

Although admin.email contains the right information, adminEmailSeq.isEmpty is always true.

Answer 1

根据说明，我假设您需要Admins Emails

val adminEmailSeq = admins.map(_.email)

Answer 2

The append ':+' actually doesn't append it to the leading Seq. It's making a copy. Regarding to your solution you would need to do this.

admins.foreach(
    admin => {
        adminEmailSeq = adminEmailSeq :+ admin.email
    }
)

But I think the right solution would be using map.

Just forgot: I'm a fan of immutables and values instead of variables. It mayhelp to understand the code much easier. Therefore I wouldn't use that variable reassigning (therefore I suggested map, as some solutions here may show you).