Question

I’m trying to create the best modeling strategy for my application and am having a problem understanding the most efficient solution.

At the top layer we have Gamers.
Gamers can have many Events.
Events have many Participants (who are Gamers).

There can be any number of Participants in an Event, which is what is throwing me off. If they were a set number of Participants I could just have them as columns inside of the Events model with a foreign key to Gamers, but I’m not sure how to setup associations for this.

My testing has them setup like so

rails gen. model Gamer ..
rails gen model Event ..
rails gen model Participants .. event:references

So now…

Event has_many :participants
Participants belongs_to :event

The problem I can’t figure out is how to link Participants to their Gamer row?

I believe it is something similar the following, but the examples in the Rails guide don’t fit my example exactly…

Gamer has_many :event_participants, :through => :events

Answer 1

I’d approach this with some relation naming changes and a join table:

class Gamer
    has_many :hosted_events, :class_name => 'Event', :foreign_key => :host_id
    has_and_belongs_to_many :events
end

class Event
    belongs_to :host, :class_name => 'Gamer'
    has_and_belongs_to_many :gamers
end

And in your DB, you’ll need the join table events_gamers, with event_id and gamer_id columns. No model, though – Rails will take care of everything behind the scenes.

You really only need the two models. Unless the relation “gamer G participated in event E” needs more data attached to it (say, “and brought chips!”) – then it would warrant its own model (I’d call it Participation – Participant is a little misleading), and the has_and_belongs_to_many relationships would become has many :throughs.

Hope this helps!