gistfile1.rb

   def update_tree(options = {}, &block)
      authorize!(action_name.to_sym, resource_class)

      
      parent_id = params[:parent_id]
      # check that parent shoud by node which is visible for the user.  
      authorize!(:list, params[:parent_id])
      
      err_exit = proc { |r| 
        render json: {
          success: false,
          msg: t('basepack.tree_list.update_tree.error', name: resource.to_label,
              msg: resource.errors.full_messages.join(',')).to_json
        }
        return #it is Proc, note we are exiting form the whole method.
      end
      
 
      resource_class.transaction do
        
        # parent id can be changed using every d & d method
        resource.parent_id = parent_id
        
        # if +position+ attribute exists, it is orderable tree
        # and position of the tree has to be set
        if resource.respond_to?(:position)

          method = params[:method]
          ancestry = resource2.ancestry

          if method == "over" # new node in subtree, set position to last
            pos = resource.siblings.order('position').last.position + 1
            resource.position = pos
            err_exit(resource) unless resource.save
          end

          # move before/after resource2
          # if moving before, position of resource2 has to be updated too
          position_cond = resource2.position
          position_cond += 1 if method == "after"

          nodes = resource2.siblings.where('position >= ?', position_cond)

          
          nodes.each do |n|
            authorize!(:update, n)
            
            position_cond += 1
            n.position = position_cond

            err_exit(n) unless n.save
          end
  
          resource.position = position_cond
  
          err_exit(resource) unless resource.save
          
        end # end transaction

        render json: { success: true }
      end