Use this class together with PlayerManager.

You may sometimes want to create teams in your game, so that some players are team mates.

A player can only belong to a single team.

class TeamManager extends Manager {
 Map<String, Bag<String>> _playersByTeam;
 Map<String, String> _teamByPlayer;

 TeamManager() {
   _playersByTeam = new Map<String, Bag<String>>();
   _teamByPlayer = new Map<String, String>();
 }

 void initialize() {}

 String getTeam(String player) => _teamByPlayer[player];

 void setTeam(String player, String team) {
   removeFromTeam(player);

   _teamByPlayer[player] = team;

   Bag<String> players = _playersByTeam[team];
   if(players == null) {
     players = new Bag<String>();
     _playersByTeam[team] = players;
   }
   players.add(player);
 }

 ReadOnlyBag<String> getPlayers(String team) {
   var result = _playersByTeam[team];
   return result == null ? null : result.readOnly;
 }

 void removeFromTeam(String player) {
   String team = _teamByPlayer.remove(player);
   if(team != null) {
     Bag<String> players = _playersByTeam[team];
     if(players != null) {
       players.remove(player);
     }
   }
 }

}