Modal window to add related records in ruby on rails

I have the following models

 class Post < ActiveRecord::Base
    ...
    has_many :tags
 end

 class Tag 开发者_开发技巧< ActiveRecord::Base
    belongs_to :post
 end

The Post controller has the typical CRUD actions plus the index. The post new view is (using simple_form and slim:

 = simple_form_for(@post) do |f|
    = f.input :title, :error => false
    = f.input :body, :as => :text, :error => false
    = f.association :tags, :include_blank => true
    div
       =link_to "Add a new tag", new_tag_path
    = custom_button "Save"
    | or 
    = link_to "Cancel", posts_path

The problem is in the "Add a new tag" link. What I would like to do is to provide a modal window with a tag creation form. Once the user has filled the form and saved the new tag, I would display back the post creation form and have the f.association :tags list updated with the newly created tag.

How should I implement this feature? It's not clear to me how to refresh only the :tag list once a new tag has been created, without loosing any other information the user may have inserted in the form (eg, post title) before creating the new tag.

Thanks.

---

may be you can go with this:

• display tag creation popup
• send AJAX request to create a tag (separate TagsController)
• display some progress indicator
• add option to 'tags' select and mark it as selected in AJAX success callback
• so everything happens without page reload

... or (if having modal window is not a requirement) use something like this: http://railscasts.com/episodes/258-token-fields :)