update a list of model instances and their associations

I have been unable to figure out how to update a list of model
instances and their associations and I have looked in the
documentation, which doesnt give an example of what I am trying to do:

http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-fields_for

I would assume this is a common task though.

I have an established association:

class AlertRule < ActiveRecord::Base

    has_many :notification_emails, :dependent => :destroy
    accepts_nested_attributes_for :notification_emails
end

class NotificationEmail < ActiveRecord::Base
  belongs_to :alert_rule
end

Controller:

def alerts_config

      //more code
      @alert_rules = alert_rules.flatten
      @alert_rules.each { |a| a.notification_emails.build }

      render :partial => 'home/alerts_config', :layout => false

View:

= form_tag '/home/save_alerts_config/' + @unit.id.to_s, :remote =>
true, :class => 'ajaxForm' do
      %table.scrollTable{:cellspacing => "0", :width =>
"740px", :style => "border-collapse: collapse; border-spacing: 0;"}
        %thead.fixedHeader
          %tr
            %th Alerts
            %th Enable
            %th Primary Email
            %th Notification Emails
            %th
        %tbody.scrollContent
          - for rule in @alert_rules
            = fields_for :alert_rules, rule do |f|
              %tr
                %td= rule.alert_code.name
                %td= check_box_tag "enabled_ids[]", rule.id
                %td= f.text_field :email, :value => rule.email, :index
=> rule.id
                %td.fields
                  = f.fields_for :notification_emails do |
notification_builder|
                    = notification_builder.text_field :email