게임에 플레이어 통계 추가

// Create the callback for our asynchronous fetch call.  This callback will
// log either an error or the average session length for the currently
// signed-in player.
gpg::StatsManager::FetchForPlayerCallback callback = [](gpg::StatsManager::FetchForPlayerResponse const &response) {
  if (IsError(response.status)) {
    LogE("An error occurred fetching player stats.");
  } else {
  gpg::PlayerStats const & player_stats = response.data;
    if (player_stats.HasAverageSessionLength()) {
      LogI("Average session length: %f", player_stats.AverageSessionLength());
    } else {
      LogW("Currently signed-in player had no associated average session length stats.");
    }
  }
};
// Asynchronously fetch the Player Stats.  When the fetch is finished it
// will call our callback. game_services_ is the std::unique_ptr<GameServices>
// returned by gpg::GameServices::Builder.Create()
game_services_->Stats().FetchForPlayer(callback);

// Asynchronously fetches the Player Stats and then logs either a
// description of them or an error
[GPGPlayerStats playerStatsWithCompletionHandler:^(GPGPlayerStats *playerStats, NSError *error) {
  if (error) {
    NSLog(@"Error fetching player stats: %@", error);
  } else {
    NSLog(@"Description of stats for the currently signed-in player: %@", playerStats);
  }
}];