Scope with join on :has_many :through association

Question

class Users < ActiveRecord::Base
  has_many :meetings, :through => :meeting_participations
  has_many :meeting_participations
end

class Meetings < ActiveRe         


        

Answer 1

Here's a one liner:

Meeting.joins(:meeting_participations).where(meeting_participation: { hidden: false, user_id: current_user.id })

This is great because you can make a scope out of it, a function out of it, or simply call it anywhere. You can also add any more restrictions you want to the hash.

Answer 2

I know this question was answered a while back but I just encountered a similar issue and was looking around for the best way to handle this. The accepted solution is very simple but I think it would be cleaner by moving the scope of the association from Users to Meeting as should below

class Users < ActiveRecord::Base
  has_many :meetings, :through => :meeting_participations
  has_many :meeting_participations
end

class Meetings < ActiveRecord::Base
  has_many :users, :through => :meeting_participations
  has_many :meeting_participations
  scope :hidden, -> { where('meeting_participations.hidden = ?', true) }
  scope :visible, -> { where('meeting_participations.hidden = ?', false) }
end

class MeetingParticipations < ActiveRecord::Base
  belongs_to :user
  belongs_to :meeting

  scope :hidden, where(:hidden => true)
  scope :visible, where(:hidden => false)
end

With this, you are able to call current_user.meetings.hidden

By design, the meeting now dictates what makes it hidden/visible.

Answer 3

It would seem to me that it is not sensible to use a scope on Meeting for your purpose. A meeting itself has no visibility, but the participation has. So I would suggest an extension on the association within User:

class User < ActiveRecord::Base
  has_many :meetings, :through => :meeting_participations do
    def visible
      ids = MeetingParticipation.
        select(:meeting_id).
        where(:user_id => proxy_owner.id, :visible => true).
        map{|p| p.meeting_id}
      proxy_target.where("id IN (?)", ids)
    end
  end
  ...
end

I hope, this helps.

Answer 4

In Rails 4, you can specify the scope originally defined in the child object in the association itself. Short: you don't have to know the internals of the MeetingParticipation model within the User model.

class User < ActiveRecord::Base
  has_many :meeting_participations
  has_many :meetings, :through => :meeting_participations
  has_many :visible_participations, -> { visible }, :class_name => 'MeetingParticipation'
  has_many :visible_meetings, :source => :meeting, :through => :visible_participations
end

class Meeting < ActiveRecord::Base
  has_many :meeting_participations
  has_many :users, :through => :meeting_participations
end

class MeetingParticipation < ActiveRecord::Base
  belongs_to :user
  belongs_to :meeting

  scope :hidden, -> { where(:hidden => true) }
  scope :visible, -> { where(:hidden => false) }
end

This would allow you to do: user1.visible_meetings and user2.visible_meetings with different result sets

Answer 5

You could also do:

current_user.meeting_participations.visible.map(&:meeting)

Answer 6

This is my solution for your problem:

class User < ActiveRecord::Base
  has_many :meeting_participations
  has_many :meetings, :through => :meeting_participations do
   def visible
     where("meeting_participations.visible = ?", true)
   end
  end
end

@user.meetings.visible