Rails - Nov 2012 - How to get which check boxes has beed unchecked and remove Subscription for them?

I have following subscription creating system, right now when I`m selection 
available subscription groups(Marketing, Sales) action Save Subscription 
create this two subscriptions:

@subscriptions = current_user.subscriptions
> @apps = App.all
> if request.post?
>   if params[:subscription] and params[:subscription][:app_id]
>     params[:subscription][:app_id].each do |app_id|
>       Subscription.create_unique({user_id: current_user.id, app_id: 
> app_id})
>     end
>     redirect_to root_path
>   end
> end
 

# app_menu.html.erb 

<%= form_for :subscription do |f| %> # this form goes to app_menu action
> above 
>
   <ul> 
>
      <% @apps.each do |app| %>
>
        <li> <%= check_box_tag app.id, current_user.access?(app)
%><span>
>
           <%= app.name %></span>
>
        </li> 
>
      <% end %>
>
    </ul> 
>
  <%= f.submit %>
>
<% end %> 
>
 
So I can only add new Subscriptions(in this particular example i can only 
add Engineering).

<http://i.stack.imgur.com/5VoyD.png>

How to refactor that action to be able also destroy subscription groups by 
uncheck them(ex. I want to unsubscribe from Marketing group) ?

So when I choose Marketing and Enginnering then 
params[:subscription][:app_id] will be equal [marketing.id, engineering.id]

Relations:

*App* 
>  has_many :subscriptions 
>  has_many :users, through: :subscriptions 
> *User* 
>  belongs_to :app 
>  has_many :subscriptions, :dependent => :destroy 
> *Subscription* 
>  belongs_to :user 
>  belongs_to :app


So the issue is how to find which apps has been unchecked? And maybe is a 
way how to refactor that action. Pleas help :)

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To view this discussion on the web visit
https://groups.google.com/d/msg/rubyonrails-talk/-/pGEodzeAsZ4J.
For more options, visit https://groups.google.com/groups/opt_out.