Rails - Jul 2006 - Has_many :through with checkboxes?

Just when I started getting the hang of has_and_belongs_to_many  
relationships, I realize that I should probably convert several of my  
app''s joins to has_many :through type relationships.

One example, pairing users with categories via subscriptions, where  
each user can be the "owner" of a category, has given me particular  
trouble when I try to update a user''s category subscriptions.

**Has anyone figured out how to manipulate HMT relationship with  
checkboxes?**

=begin code

## Here''s what my models look like:

## user.rb
has_many  :subscriptions
has_many  :cats, :through => :subscriptions

## cat.rb
has_many :subscriptions
has_many :users, :through => :subscriptions

## subscription.rb
belongs_to :user
belongs_to :cat

## In the view, I can display a user''s subscriptions as a set of  
checkboxes just fine:

## cats.rhtml
<% cats.each do |cat| %>
   <%= check_box_tag("cats[]", cat.id, @user.cats.include?(cat)) % 
 ><label>cat.name</label>
<% end %>

## It''s the controller method''s that foul me up
## I believe I should clear out a user''s subscriptions on submit
## (to account for unchecked boxes and to start from scratch for the  
next step) and then
## I should add a subscription for each checked box

## this doesn''t work, but it''s what I''m hacking on
now--HELP! :-)

# account_controller.rb
@user = User.find(params[:id])

subscriptions = Subscription.find(:all, :conditions => "user_id =  
@user")
subscriptions.each do |subscription|
   subscription.destroy
end

categories = params[:cats]
categories.each {|cat|
   subscription = Subscription.new(:cat_id=>cat, :user_id=>@user)
   subscription.save
}

=end code

Does anyone know what''s going wrong here?

Very grateful for your help,

Jacob

-
Jacob Patton

I think I maybe sorted out the update script.  Here''s what I have now:

= begin
# user.rb
has_many  :subscriptions, :dependent => true
has_many  :cats, :through => :subscriptions

# cat.rb
has_many :subscriptions, :dependent => true
has_many :users, :through => :subscriptions

# subscription.rb
belongs_to :user
belongs_to :cat

# account_controller.rb#cats
   def cats
     @user = User.find(params[:id])
     @cats = Cat.find(:all)
     if request.post?
       # clear user subscriptions
       @user.subscriptions.clear
       # if cats param is set (not nil), create the subscriptions
       if params[:cats]
         categories = params[:cats]
         categories.each {|cat|
           sub = Subscription.create(:user_id => @user, :cat_id => cat)
           sub.save
         }
       end
       flash[:notice] = "Category subscriptions updated."
       redirect_to :action => :cats, :id => @user
     end

=end

That all seems to work!  I hope this helps someone!

Best,

Jacob

-
Jacob Patton

On Jul 4, 2006, at 12:05 PM, Jacob Patton wrote:
> Just when I started getting the hang of has_and_belongs_to_many  
> relationships, I realize that I should probably convert several of  
> my app''s joins to has_many :through type relationships.
>
> One example, pairing users with categories via subscriptions, where  
> each user can be the "owner" of a category, has given me
particular
> trouble when I try to update a user''s category subscriptions.
>
> **Has anyone figured out how to manipulate HMT relationship with  
> checkboxes?**
>
> =begin code
>
> ## Here''s what my models look like:
>
> ## user.rb
> has_many  :subscriptions
> has_many  :cats, :through => :subscriptions
>
> ## cat.rb
> has_many :subscriptions
> has_many :users, :through => :subscriptions
>
> ## subscription.rb
> belongs_to :user
> belongs_to :cat
>
> ## In the view, I can display a user''s subscriptions as a set of  
> checkboxes just fine:
>
> ## cats.rhtml
> <% cats.each do |cat| %>
>   <%= check_box_tag("cats[]", cat.id,
@user.cats.include?(cat)) %
> ><label>cat.name</label>
> <% end %>
>
> ## It''s the controller method''s that foul me up
> ## I believe I should clear out a user''s subscriptions on submit
> ## (to account for unchecked boxes and to start from scratch for  
> the next step) and then
> ## I should add a subscription for each checked box
>
> ## this doesn''t work, but it''s what I''m hacking
on now--HELP! :-)
>
> # account_controller.rb
> @user = User.find(params[:id])
>
> subscriptions = Subscription.find(:all, :conditions => "user_id =  
> @user")
> subscriptions.each do |subscription|
>   subscription.destroy
> end
>
> categories = params[:cats]
> categories.each {|cat|
>   subscription = Subscription.new(:cat_id=>cat, :user_id=>@user)
>   subscription.save
> }
>
> =end code
>
> Does anyone know what''s going wrong here?
>
> Very grateful for your help,
>
> Jacob
>
> -
> Jacob Patton