Liftweb's IfLoggedIn implementation

IfLoggedIn.scala

/*
 * IfLoggedIn implementation which redirects to the page a user was going to,
 * after his/her successful login
 *
 * based on http://groups.google.com/group/liftweb/browse_thread/thread/bdd5accd4bb623c9/d56e054c4037470f ,
 * works with ProtoUser out of the box
 */

// In SiteMap:
lazy val IfLoggedIn = If(User.loggedIn_? _, loginAndComeBack _)

private def loginAndComeBack = {
  val uri = S.uri
  RedirectWithState(loginUri, RedirectState( () => User.goAfterLogin(uri), ?("notlogged") -> NoticeType.Notice ) )
}

private lazy val loginUri = SiteMap.findLoc("Login").map{ _.link.uriList }.
  openOr(LiftRules.siteMapFailRedirectLocation).mkString("/", "/", "")


// In User model object:
object goAfterLogin extends SessionVar("/")

override def homePage = {
  val uri = goAfterLogin.is
  goAfterLogin.remove
  uri
}