Question

I’m still having trouble building complex joins in ActiveRecord.

I have a User model that is using the HasManyFriends plugin by Steve Ehrenberg (http://dnite.org).

Then I have a UserFeedEvent model that links users to a FeedEvent model.

What I’d like to achieve is to find all the FeedEvents linked to the friends of a User.

How should I write my ActiveRecord query?

Here are my models:

class User < ActiveRecord::Base

  has_many_friends

  has_many :feed_events, :through => :user_feed_events, :dependent => :destroy
  has_many :user_feed_events, :dependent => :destroy

end


class UserFeedEvent < ActiveRecord::Base

  belongs_to :feed_event, :dependent => :destroy
  belongs_to :user

end


class FeedEvent < ActiveRecord::Base
  has_many :user_feed_events, :dependent => :destroy
  has_many :users, :through => :user_feed_events

  serialize :data
end

Thanks in advance!
Augusto

Answer 1

I found a working and more traditional SQL solution:

friends_id = current_user.friends.collect {|f| f.id}.join(",")

sql = "SELECT feed_events.*, user_feed_events.user_id  FROM feed_events LEFT JOIN user_feed_events ON feed_events.id = user_feed_events.feed_event_id WHERE user_feed_events.user_id IN (#{friends_id}) GROUP BY feed_events.id ORDER BY feed_events.created_at DESC"

friend_feed_events = FeedEvent.paginate_by_sql(sql, :page => params[:page], :per_page => 30)

If you have a more efficient / more elegant way of doing the same, please let me know!