アプリがアクティブになったタイミングでGame CenterのLeaderboardからスコアを取得する

// add notification observer. When the App staus becomes active, works using block
NotificationCenter.default.addObserver(
    forName: UIApplication.didBecomeActiveNotification,
    object: nil,
    queue: OperationQueue.main,
    using: { _ in
        print("App status becomes active.")
        self.didBecomeActive()
    }
)

private func didBecomeActive() {
    print("didBecomeActive.")
    loadScore(scoreDidLoad: { local, entries in
    // If entries are loaded, set the value to worldHighScore
        if let entries = entries,
            entries.isEmpty == false {
            self.autoLoadScore2.worldScore = entries[0].score
        }
        // If local is loaded, set the value to yourHighScore
        if let local = local {
            self.autoLoadScore2.yourScore = local.score
        }
    })
}

private func loadScore(scoreDidLoad: @escaping (_ localPlayerEntry: GKLeaderboard.Entry?, _ entries: [GKLeaderboard.Entry]?) -> Void) {
    print("func loadScore")
    if GKLocalPlayer.local.isAuthenticated {
        print("You are logged in. Start to load scores from Game Center.")
        // Get the Leaderboard ID of this app that you have previously registered in App Store Connect
        // (only one ID is registered here).
        GKLocalPlayer.local.loadDefaultLeaderboardIdentifier(completionHandler: { (leaderboardIdentifer, error) in
            if error != nil { // Error occured
                print(error!.localizedDescription)
            } else { // Got the loaderBoarderIdentifier for this app.
                // Load scores
                if let leaderboarderId = leaderboardIdentifer {
                    print("Default leaderboardIdentifer is \(leaderboarderId).")
                    GKLeaderboard.loadLeaderboards(IDs: [leaderboarderId]) { (boards, _) in
                        boards?.first?.loadEntries(for: .global, timeScope: .allTime, range: NSRange(location: 1, length: 1), completionHandler: {(myLocalPlayerEntry, myEntries, _, _) in
                            scoreDidLoad(myLocalPlayerEntry, myEntries)
                        })
                    }
                }
            }
        })
    }
}