validate_by_6pp.rb

# config/environment.rb
require "open-uri"
config.gem "nokogiri"


# app/models/your_model.rb
# Expects postal_code, street and city to be part of your model:
#  Address.postal_code = "1222 AX"
#  Address.street = "Erfgooiersstraat"
#  Address.city = "Hilversum
# Address validation based on the postal_code database from 6pp (http://kvdb.net/projects/6pp/):
# - streetname in the 6pp database should match Address.street
# - cityname in the 6pp database should match Address.city
validate :valid_address

def valid_address
  valid_city = valid_street = false

  if postal_code =~ /^[1-9]{1}[0-9]{3} ?[A-Z]{2}$/
    pc = postal_code.gsub(/ /,"")
    sixpp = Nokogiri::HTML(open("http://6pp.kvdb.net/services/lookup?postcode=#{pc}"))
    sixpp.xpath("//city").each {|c| 
      valid_city = true if !c.content.empty? && city =~ /^#{c.content}/i
    }
    sixpp.xpath("//street").each {|s|
      valid_street = true if !s.content.empty? && street =~ /^#{s.content}/i
    }
  end
  errors.add(:city, "doesn't match postal code") unless valid_city
  errors.add(:street, "doesn't match postal code") unless valid_street
end