fab-manager/app/models/custom_asset.rb

class CustomAsset < ActiveRecord::Base
  has_one :custom_asset_file, as: :viewable, dependent: :destroy
  accepts_nested_attributes_for :custom_asset_file, allow_destroy: true

  # static method to retrieve the attachement URL of the custom asset
  def self.get_url(name)
    asset = CustomAsset.find_by(name: name)
    asset.custom_asset_file.attachment_url if asset and asset.custom_asset_file
  end

  after_update :update_stylesheet if :viewable_changed?

  def update_stylesheet
    if %w(profile-image-file).include? self.name
      Stylesheet.first.rebuild!
    end
  end
end