Question

I am trying to create the following:

User model (this is fine)

id

Link model (associated with two Users)

id
user_id1
user_id2

Is this an instance in which I would want to use the has_and_belongs_to_many association type on the Link model? How should I do this?

Ultimately, I would like to be able to have a user object and call @user.links to get all links involving that user…

I’m just not sure what the best way to do this in Rails is.

Answer 1

You will very likely want two models structured as follows:

class User < ActiveRecord::Base
  has_many :friendships
  has_many :friends, :through => :friendships #...
end

class Friendship < ActiveRecord::Base
  belongs_to :user
  belongs_to :friend, :class_name => 'User', :foreign_key => 'friend_id'
end 

# ...and hence something like this in your view
<% for friendship in @user.friendships %>
  <%= friendship.status %>
  <%= friendship.friend.firstname %>
<% end %>

(This pattern is from a post made by Ryan Bates about two years ago during this discussion on RailsForum.)

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Just a note: this is now quite old. You may want to consider evaluating other strategies for handling this in a modern Rails context.