Why isn't Rails recognizing nil if blank in my form? -

i'm reworking rails 2 website. right now, i'm getting error, , think it's because value being submitted blank instead of .nil. however, attempts keep nil don't seem working. appreciate have offer.

from model, based on make blank params[] nil

    null_attrs = %w( start_masterlocation_id )     before_save :nil_if_blank      protected      def nil_if_blank     null_attrs.each { |attr| self[attr] = nil if self[attr].blank? }     end 

view

i've got jquery adds value hidden field when start_masterlocation_id exists. i've got jquery removes field attribute when not exist.

    <%= hidden_field :newsavedmap, :start_masterlocation_id, :id => "start-masterlocation-id-field" %> 

finally, here part of controller throwing error. controller page holds form (maptry), not controller newsavedmap. think have delete @newsavedmap.id, @newsavedmap.mapname, , @newsavedmap.optimize lines i'm going form handlers, don't think that's related error.

controller

    def maptry     @itinerary = itinerary.find(params[:id])     if @itinerary.user_id == current_user.id     respond_to |format|     @masterlocation = masterlocation.find(:all)     format.html     end     format.xml  { render :xml => @masterlocation }     format.js     @masterlocation = masterlocation.find(:all)     render :json => @masterlocation.to_json(:only => [:id, :nickname, :latitude, :longitude])     end     end     if params[:newsavedmap_id]     @newsavedmap = newsavedmap.find(:first, :conditions => {:id => params[:newsavedmap_id]})     @waypoint = waypoint.find(:all, :conditions => {:newsavedmap_id => params[:newsavedmap_id]})     @newsavedmap.id = params[:newsavedmap_id]     @newsavedmap.mapname = newsavedmap.find(:first, :conditions => {:id => params[:newsavedmap_id]}).mapname     @newsavedmap.optimize = newsavedmap.find(:first, :conditions => {:id => params[:newsavedmap_id]}).optimize     if !@newsavedmap.start_masterlocation_id.nil?            @start_name = masterlocation.find(:first, :conditions => {:id => @newsavedmap.start_masterlocation_id}).name     end     if !@newsavedmap.end_masterlocation_id.nil?          @end_name = masterlocation.find(:first, :conditions => {:id => @newsavedmap.end_masterlocation_id}).name     end     else     @newsavedmap = newsavedmap.new       end     else     redirect_to '/'     end     end 

error not occur when start_masterlocation_id present in database.

    undefined method `name' nil:nilclass 

i solved ignoring nil problem. instead, used

    !@newsavedmap.start_masterlocation_id.blank?  

this evaluates whether data in record blank , either or doesn't something. obviously, results in unwanted "blank" data being left inside database, it's not ideal, helped me move forward project. i'd appreciate responses deal directly nil issue , tell me how have rails ignore blank data in form.