form_for (ActionView::Helpers::FormHelper)

    # File lib/action_view/helpers/form_helper.rb, line 123
          def form_for(object_name, *args, &proc)
            raise ArgumentError, "Missing block" unless block_given?
            options = args.last.is_a?(Hash) ? args.pop : {}
            concat(form_tag(options.delete(:url) || {}, options.delete(:html) || {}), proc.binding)
            fields_for(object_name, *(args << options), &proc)
            concat('</form>', proc.binding)
          end