Question

So I have a rails app That lets users create lists and put items on that list. As a feature a user can put any one item on multiple lists. Example:

List_1
  -item_1
  -item_2

List_2
  -item_3
  -item_2

The relationship side of it all is complete and working fine.

The next step was to let the user arrange the items in their lists. I installed act_as_list and using jQuery sortable got a simple drag and drop working for sorting items. The issue is each item has one position. So if I change item_2’s position to 1 on list_1, item_2’s position is now 1 in every list.

I’m trying to think of a way to store item positions relative to the list. Anyone have any thoughts?

Edit to Add code

List model

class List < ActiveRecord::Base
  belongs_to :user

  has_many :assignments, dependent: :destroy
  has_many :items, through: :assignments, order: 'position'

end

Item model

class Item < ActiveRecord::Base
  belongs_to :user

  has_many :assignments, dependent: :destroy
  has_many :lists, through: :assignments
  acts_as_list scope: :list
end

Assignment model

class Assignment < ActiveRecord::Base
  belongs_to :item
  belongs_to :list

  validates_uniqueness_of :item_id, :scope => :list_id
end

Answer 1

So an answered my own question with a little time an effort. I’ve provided an example below for anyone who may run into the issue in the future.

Basically @thedeeno’s answer would have worked fine if I was able to use scopes. In my case the list will be user created and hence scopes are not an option.

Solution:
So my solution was adding a position column to my assignments table (the join table for my has many through)

This way each assignment could now have a list_id and item_id and a position.

Then in my controller I did the following to populate the @items hash

@items = @list.items.order(:position)

This gave makes @item has ordered by item positions for their respective list position.

Now the last step was updating their position using sortable. To update the correct item’s postion I needed sortable to send the list_id along with each order of the id’s. To get the list_id sent with the post I adding a hidden li with and id of the @list like so

<li id='list_<%=@list.id %> style='display:none'></li>

which meant that my params now looked like this

{"list"=>["31"], "item"=>["30", "58", "59", "24", "80", "81"]}

Finally using the skills I had learned from http://railscasts.com/episodes/147-sortable-lists I changed my sort action to the following

def sort
  @items = params[:item]

  @items.each_with_index do |id, index|
    assignment = Assignment.where(list_id: params[:list], item_id: id).update_all(['position=?', index+1])
  end

render :nothing => true
end

That’s it! users can now create any number of lists and item to multiple lists and sort each list independently. Hope this helps someone!