Rails: add asterix to required fields

form_builder.rb

class ActionView::Helpers::FormBuilder
  alias :orig_label :label

  # add a '*' after the field label if the field is required
  def label(method, content_or_options = nil, options = nil, &block)
    if content_or_options && content_or_options.class == Hash
      options = content_or_options
    else
      content = content_or_options
    end

    content ||= I18n.t("activerecord.attributes.#{object.class.name.underscore}.#{method}", :default => method.to_s.humanize)
    if (options.nil? || options[:without_asterix] != true) && object.class.validators_on(method).map(&:class).include?(ActiveModel::Validations::PresenceValidator)
      content += ' <em class="required">*</em>'
    end

    self.orig_label(method, content.html_safe, options || {}, &block)
  end
end