rails: rendering content

gistfile1.rb

content = ''
@fields_group.each do |fg|
  content << @template.content_tag(:div, class: 'fields-group') do
    @template.concat(@template.content_tag(:div, class: 'fields-group__header') do
      @template.concat @template.content_tag(:h3, fg.label, class: 'fields-group__header-title')
    end)
    @template.concat(@template.content_tag(:div, class: 'fields-group__body') do
      fg.fields.each { |f| @template.concat @template.content_tag(:span, f.name, class: 'fields-group__field') }
    end)
  end
end
content.html_safe