manufacturer.rb

class Manufacturer < ActiveRecord::Base
  def self.selectable
    result = []
    result << self.joins(:cars).joins(cars: :basic_articles).where(published: true, cars:{published: true}, basic_articles: {published: true, requires_extra: false}).map{ |r| r.id }
    result << self.joins(:cars).joins(cars: :basic_articles).joins(cars: [basic_articles: :extras]).where(published: true, cars:{published: true}, basic_articles: {published: true, requires_extra: true}).map{ |r| r.id }
    return self.where(id: result)
  end
end