XML : Ruby on Rails passing view variable to model and back

Hi I have difficult times to understand why I get # instead of correct value

View:

  <%= form_tag root_url, method: :get do %>  <p>   <%= text_field_tag :zip_code, params[:zip_code] %>    <%= submit_tag "Lookup", name: nil %>   </p>  <% end %>      <% if @zip_code %>    <dl id ="zip_info">      <dd> <%=  @zip_code %> </dd>    </dl>   <% end %>    

Model:

  class ZipCode < ActiveRecord::Base      def initialize(zip)         return zip      end         end    

Controller:

  class ZipCodeLookupController < ApplicationController     def index       @zip_code = ZipCode.new(params[:zip_code]) #(params[:zip_code]) if params[:zip_code].present?     end  end