module Relationable
  extend ActiveSupport::Concern

  included do
    has_many :related_contents, as: :parent_relationable, dependent: :destroy
  end

  def find_related_content(relationable)
    RelatedContent.where(parent_relationable: self, child_relationable: relationable).first
  end

  def relationed_contents
    related_contents.not_hidden.map { |related_content| related_content.child_relationable }
  end
end