Address standardization via USPS Webtools API

gistfile1.rb

require 'rubygems'
require 'nokogiri'
require 'open-uri'

module USPS
  SERVER = "http://production.shippingapis.com/ShippingAPITest.dll"
  USERNAME = 'username-here' # username from http://www.usps.com/webtools/

  class Address
    # requres ruby-1.9, which keeps hashes ordered
    # @@attr_tags = {}
    # [:firm_name, :address1, :address2, :city, :state, :zip5, :zip4].each do |a|
    #   attr_accessor a
    #   @@attr_tags[a] = a.to_s.capitalize.gsub(/_(.)/) { $1.upcase }
    # end

    @@attr_tags = []
    [:firm_name, :address1, :address2, :city, :state, :zip5, :zip4].each do |a|
      attr_accessor a
      @@attr_tags << [a, a.to_s.capitalize.gsub(/_(.)/) { $1.upcase }]
    end

    def initialize(options = {})
      options.each_pair do |k, v|
        self.send("#{k}=", v)
      end
    end

    def standardize
      # Generate the URI from this Address.
      uri = USPS::SERVER + '?API=Verify&XML=<AddressValidateRequest ' +
            'USERID="' + USPS::USERNAME + '"><Address ID="0">'
      @@attr_tags.each do |a, t|
        val = self.instance_variable_get "@#{a}"
        uri += '<' + t + '>' + val.to_s + '</' + t + '>'
      end
      uri += '</Address></AddressValidateRequest>'

      # Send the request synchronously and parse the response document.
      doc = Nokogiri::XML(open(URI.encode(uri)))
      if (error = doc.at_css('Error')) # handle error
        message = error.at_css("Description").text
        code = error.at_css('Number').text
        source = error.at_css('Source').text
        raise StandardError, "#{message} #{code} #{source}"
      else # handle OK responses
        address = Address.new
        root = doc.at_css('Address')
        @@attr_tags.each do |a, t|
          if (node = root.at_css(t)) then address.send("#{a}=", node.text) end
        end
        address # return address
      end
    end
  end
end

puts USPS::Address.new({
  :address2 => '6406 Ivy Lane',
  :city => 'Greenbelt',
  :state => 'MD'
}).standardize.inspect