acts_as_list problem with scope - ruby-on-rails

Question

The problem I have is at the bottom.
Models:
class Skill
has_many :tags
acts_as_list :column => 'sequence'
end
class Tag
belongs_to :skill
acts_as_list :column => 'sequence', :scope => :skill
end
View:
<table id="skills">
<% #skills.each do |s| %>
<tr id="skill_<%= s.id %>">
<td>
<%= s.name %>
</td>
<td>
<ul id="tags">
<% s.tags.each do |t| %>
<li id="tag_<%= t.id %>">
<%= t.name %>
</li>
<% end %>
</ul>
</td>
</tr>
<% end %>
</table>
jQuery for drag and drop:
$( "#skills" ).sortable({
axis: 'y',
dropOnEmpty: false,
handle: '.handle',
cursor: 'move',
items: 'tr',
opacity: 0.4,
scroll: true,
update: function(){
$.ajax({
type: 'post',
data: $('#skills').sortable('serialize') + "&authenticity_token=" + "<%= form_authenticity_token %>",
dataType: 'script',
complete: function(request){
$('#skills').effect('highlight');
},
url: '<%= url_for :action => 'sort', :controller => 'skills' %>'
})
}
});
$( "#tags" ).sortable({
axis: 'y',
dropOnEmpty: false,
handle: '.handle',
cursor: 'move',
items: 'li',
opacity: 0.4,
scroll: true,
update: function(){
$.ajax({
type: 'post',
data: $('#tags').sortable('serialize') + "&authenticity_token=" + "<%= form_authenticity_token %>",
dataType: 'script',
complete: function(request){
$('#tags').effect('highlight');
},
url: '<%= url_for :action => 'sort', :controller => 'tags' %>'
})
}
});
Controller for Tags:
def sort
#tags = Tag.all
#tags.each do |tag|
tag.sequence = params['tag'].index(tag.id.to_s) + 1
tag.save
end
render :nothing => true
end
PROBLEM:
After dragging the tags there is an error:
NoMethodError (You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.+):
app/controllers/tags_controller.rb:12:in `block in sort'
app/controllers/tags_controller.rb:11:in `each'
app/controllers/tags_controller.rb:11:in `sort'
I found the error is gone if I load tags belonging to a specific Skill like this:
def sort
#tags = Skill.find(1).tags
Question - how to tell the controller which tags to load (but not all tags)?
A SOLUTION I FOUND...
Tags controller:
def sort
#tag = Tag.find(params[:tag]).first
#skill = Skill.find_by_id(#tag.skill_id)
#tags = #skill.tags
Is this the best way to do it?

Answer 1

The error occurred while evaluating nil.+):
This means that whatever params['tag'].index(tag.id.to_s) + 1 (from sort in controller) is supposed to do is actually resulting in nil + 1.
If your solution performs as expected, then I don't see a problem with it.
As a tip, #skill = Skill.find_by_id(#tag.skill_id) could be shortened to #skill = #tag.skill if you do belongs_to :skill in your Tag model.