Rails habtm query based on a condition

Question

I have following associations:

class ConferenceSession < ActiveRecord::Base

  has_many :conference_sessions

end


class ConferenceSession < ActiveRecord::Base

  belongs_to  :conference

  has_and_belongs_to_many  :users

end

class User < ActiveRecord::Base

  has_and_belongs_to_many :conference_sessions

end

and a conference_sesssions_users table. Admin can allow specific people to attend a particular session. So I want to form a query that whenever a user logs in and selects a conference he should be allowed to see only those sessions where the admin has allowed him to. I tried this:

scope :visibility,
    lambda { |user_id| joins(:conference_sessions_users).where('conference_sessions_users.user_id = ?' => user_id) }

but I'm getting an error ActiveRecord::ConfigurationError: Association named 'conference_sessions_users' was not found on ConferenceSession; perhaps you misspelled it? ActiveRecord::ConfigurationError: Association named 'conference_sessions_users' was not found on ConferenceSession; perhaps you misspelled it?

What could be wrong?

Answer 1

The error is referring to the joins(:conference_sessions_users) part of your scope. For the joins argument "The given symbol(s) should match the name of the association(s)."

You've used the name of the join table which isn't right in this situation.

To use the association you'd need: joins(:user)

If you do just want to use the joining table you can use a string to define the join:

joins("inner join conference_sessions_users
       on conference_session_id = conference_sessions.id")