file_name.rb

  def file_names
    super.try(:split, ',').to_a
  end

  #
  def file_names=(value)
    joined_value = value.join(',')
    super(joined_value)
  end

  def file_names<< (value)
    if file_names.empty?
      file_names = value
    else
      file_names = file_names + [value]
    end
  end
  alias push <<