XML : pass variable from view to controller and then model

I want to use xml soap later but at first I am trying to just get an input from input and send it to model via controller. I have difficult time to get this first step done. here are my code:

View (index.html.erb)

   <%= form_tag(:controller => "zip_code_lookup", :action => 'index') do  %>      <%= text_field_tag :zip_code, params[:zip_code] %>      <%= submit_tag("go") %>   <% end %>      <h3>Displaying: <%= @zip_code %></h3>    

Controller

   class ZipCodeLookupController < ApplicationController      def index           @zip_code = ZipCode.initialize(@zip_code)        end      end    

Model:

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