A quick module for doing postal code lookups from the geonames.org JSON API.

postal_code_lookup.rb

require 'multi_json'

module PostalCodeLookup
  GEONAMES_URL = 'http://api.geonames.org/postalCodeSearchJSON'

  def self.find_postal_code_data(code)
    info = nil

    begin
      client = HTTPClient.new

      query = {
        'postalcode' => code,
        'maxRows' => 1,
        'username' => 'demo',
        'country' => 'US'
      }

      res = client.get(GEONAMES_URL, query)

      if res.status == 200 && res.contenttype =~ /application\/json/
        hash = MultiJson.load(res.content)

        unless hash["postalCodes"].nil? || hash["postalCodes"].empty?
          info = {}
          info[:zip] = code
          info[:state] = hash["postalCodes"].first["adminName1"]
          info[:short_state] = hash["postalCodes"].first["adminCode1"]
          info[:city] = hash["postalCodes"].first["placeName"]
        end
      end
    rescue => e
      Rails.logger.error e.message
      Rails.logger.error e.backtrace.join("\n")
      info = nil
    end

    return info
  end
end