Question

I don’t know if this is right place. But I need answer very much.

I’m writing program for tournament management. I have simple problem but for me it is not that clear.

There are many clubs (One club from one city). There are players in club. There are no players without club.

I have Player class and Club class.
Should I keep list of players in Club class or keep players club in his class?
Which way would be better?

Answer 1

Since every Player has a Club, keep a list of Players in the Club class. This makes it fast and simple to enumerate or search all Players in a given Club. However, there’s no reason you can’t also have a reference in the Player class which points to its parent Club. There are valid use cases for having a link in each direction, so do both.

I’m assuming that each Player can only belong to one Club. Things will get a bit more complicated if that is not the case.

An example in C#: (not compiled / tested, so it may have some minor errors)

public class Club
{
   // other class members

   // this is private so that code must use Club's methods to get at the Players
   private List<Player> _players;

   public int PlayerCount
   {
      get
      {
         return _players == null ? 0 : _players.Count;
      }
   }

   public void AddPlayer(Player p)
   {
      // null checking etc
      // here you could enforce a rule that p.ParentClub must be null
      // to prevent a Player from being in multiple Clubs
      p.ParentClub = this;
      _players.Add(p);
   }

   public void RemovePlayer(Player p)
   {
      // null checking etc
      _players.Remove(p);
      p.ParentClub = null;
   }
}

public class Player
{
   // other class members

   public Club ParentClub 
   { get; set; }
}

Now, you can do things like this:

// add Player Joe to the London Club if it is not full (10 members max)
// otherwise add Joe to the Munich Club
if(londonClub.PlayerCount <= 10)
{
   londonClub.AddPlayer(joePlayer);
}
else
{
   munichClub.AddPlayer(joePlayer);
}

// print how many players are in the club that Joe is in
Console.WriteLine("Number of Players in Joe's Club: " + joePlayer.ParentClub.PlayerCount.ToString());

// move Joe to the Amsterdam club. Note that it does not matter what Club Joe was already in
joePlayer.ParentClub.RemovePlayer(joePlayer);
amsterdamClub.AddPlayer(joePlayer);