// if player is logged in to GC,then report the score
if GKLocalPlayer.localPlayer().authenticated {
    let gkscore = GKscore(leaderboardIdentifier: "leaderBoardID")
    gkscore.value = score
    GKscore.reportscores([gkscore],withCompletionHandler: ( { (error: NSError!) -> Void in
        if (error != nil) {
            // handle error
            println("Error: " + error.localizedDescription);
        } else {
            println("score reported: \(gkscore.value)")
        }
    }))
}