Postoffice

gem install postoffice

or add the following to your Gemfile

gem 'postoffice'

To validate various world postal codes:

class MyClass < ActiveRecord::Base
  validates :postcode, :postcode_format => {:country_code => :us, :message => "entered is not a valid postcode for #{PostOffice.country_name(options[:country_code])}."}
end

To validate Canadian postal codes, simply change the symbol :us to :ca, and you'll get:

Note: Don't forget to use the ':allow_blank => true' option, when needed.

Country name codes abide by the ISO 3166-1 alpha-2 standard. 155 countries are supported: see COUNTRYCODES.md for the full list.

Validating correctness of postcodes directly:

# Validating an English postcode. Returns 0, since this postcode is valid, returns nil otherwise
PostOffice.validate_postcode('N1 9GU', :gb)

To produce a string of the name of a country, input a supported 2-digit country code as a symbol.

Example:

PostOffice.country_name(:us)

This will output "United States".

PostOffice.country_name(:lu)

This will output "Luxembourg".

See the LICENSE file.