Fixing OCP with abstract factory

class Report
  def output
    formatter =
      case @format
      when :html
        HtmlFormatter.new(self)
      when :pdf
        PdfFormatter.new(self)
        # ...etc
      end
  end
end

class Report
  def output
    formatter_class =
      begin
        @format.to_s.classify.constantize
      rescue NameError
        # ...handle 'invalid formatter type'
      end
    formatter = formatter_class.send(:new, self)
    # etc
  end
end