2 belongs_to, 1 has_many : Team/Game relationship

Question

I have two models Game and Team:

    class Game < ActiveRecord::Base
      belongs_to :home_team, class_name: 'Team', required: true
      belongs_to :visitor_team, class_name: 'Team', required: true
    end

and

    class Team < ActiveRecord::Base
      has_many :games
    end

The relationship has_many :games doesn't work (I would have to specify class_name but in this case I have two class names). I have to differentiate home and visitor.

Any idea on how to design this?

Thanks

Yang · Answer 1 · 2015-12-21T18:29:34.850

0

You have to specify the foreign_key, assuming you have columns home_team_id and visitor_team_id in games table:

has_many :home_games, class_name: 'Game', foreign_key: :home_team_id
has_many :visitor_games, class_name: 'Game', foreign_key: :visitor_team_id

edited Dec 21 '15 at 18:29

answered Dec 21 '15 at 18:21

Yang

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This is wrong. It has nothing to do with the declaration of `belongs_to`. – user229044 Dec 21 '15 at 18:24
Hi, thanks for your response. However the foreign_key doesn't change anything here. I'm still getting "SQLException: no such column: games.team_id". I think the issue is probably in the declaration of has_many but I don't know what's missing. – Dec 21 '15 at 18:25
Sorry, copied the wrong lines to edit... I have updated my answer. – Yang Dec 21 '15 at 18:30

score 0 · Answer 2 · answered Dec 21 '15 at 18:26

has_many will look for a foreign key with the same name as the class you're working in.

In this case, Rails will assume there is a team_id in the associated Game class, linking back to the Team.This isn't the case, so you need to be more explicit.

In this case, you also don't have a single link from a Game back to a Team. There are two different links between Game and Team, so you need to represent both of these links as associations:

class Team < ActiveRecord::Base
  has_many :home_games, class_name: 'Game', foreign_key: :home_team_id
  has_many :visitor_games, class_name: 'Game', foreign_key: :visitor_team_id
end

If you want to get all games for a given team, regardless of whether they are home or visitng games, you can define a method:

class Team < ActiveRecord::Base
  has_many :home_games, class_name: 'Game', foreign_key: :home_team_id
  has_many :visitor_games, class_name: 'Game', foreign_key: :visitor_team_id

  def games
    Game.where('home_team_id = ? or visitor_team_id = ?', id, id)
  end
end

Thanks! :) That's exactly what I currently have but I was hoping to replace my "games" method by a pretty has_many. — , Dec 21 '15 at 18:31

2 belongs_to, 1 has_many : Team/Game relationship

2 Answers2