Some associations code that doesn't want to work.

rails_associations_rocks.rb

class GroupCalendar < Calendar     # Calendar inherits ActiveRecord:Base
  has_and_belongs_to_many :users

  has_many :sub_inheritances
  # has_many :sub_calendars, through: :sub_inheritances, as: :calendarable # <- this line should be as the following:
  has_many :sub_calendars, through: :sub_inheritances, source: :calendarable, source_type: :Calendar

end

class SubInheritance < ActiveRecord::Base
  belongs_to :group_calendar
  belongs_to :calendarable, polymorphic: true
end

class CreateSubInheritances < ActiveRecord::Migration
  def change
    create_table :sub_inheritances do |t|
      t.integer :group_calendar_id
      t.references :calendarable, polymorphic: true

      t.timestamps
    end
  end
end

# When I try to 'group_calendar.sub_calendars' in the rails console I get: 
# "ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) :sub_calendar or :sub_calendars in model SubInheritance. Try 'has_many :sub_calendars, :through => :sub_inheritances, :source => <name>'. Is it one of :group_calendar or :calendarable?"