better nested set and parent_id

Hello everybody

I have a model with better_nested_set. In my "new" form, i pass the desired parent_id as a hidden field, and in the create action at the controller i save the new register and use move_to_child_of Model (params[item][parent_id])

Everything works, but at my log file it warns that i can't mass asign the property "parent_id".

What can i do to avoid the warning?

Here is my controller's update action:

  def create     @invite =[:invite])     begin       @parent_invitee = Invite.find_by_id(params[:invite][:parent_id])     rescue Exception => exc         logger.error("Invalid parent_id: #{exc.message}")         render :action => "new"     end     respond_to do |format|       if         @invite.move_to_child_of(         flash[:notice] = 'Invite was successfully created.'         format.html { redirect_to :action => "show", :id => @invite.confirmation_code }         format.xml { render :xml => @invite, :status => :created, :location => @invite }        else           format.html { render :action => "new" }           format.xml { render :xml => @invite.errors, :status => :unprocessable_entity }         end       end   end