Rails - Mar 2006 - handle multiple lists: move an item from one list to another

How do I manage multiple lists?

This is what I need. Sometimes an item needs to be moved from one list 
to another.

class Item < ActiveRecord::Base
  belongs_to :group
  acts_as_list :scope => :group
end

class Group < ActiveRecord::Base
  has_many :items, :order => "position"
end


Now, sometimes, I may need to change an item from one group to another. 
But when I do that, the position number is not corrected. I end up 
having multiple items in a group with the same position.

What is the correct way to handle something like this?
Thanks for your help.
Arpan

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I''ve had the same problem. It seems that acts_as_list doesn''t
updates
positions when scope changes.
I tried to set up a callback method before_validation_on_update in the 
model, like so :

class Item < ActiveRecord::Base
  belongs_to :group
  acts_as_list :scope => :group

before_validation_on_update :reorder_positions

	private

	def reorder_positions
		@updated_group_id = params[:person][:group_id]
		unless @updated_group_id == self.group_id
			self.move_to_bottom # reorder original list
			params[:item][:position] = 
Group.find_by_id(@updated_group_id).items.length + 1
		end
	end
end

Unfortunately it doesn''t work, somehow the model throws an error on 
accessing the params hash.

So I solved this at the controller level, in the update method.

It works but I''m concerned about breaking the MVC, such a reordering 
should happen in the model.

Bernard.

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