Subdomain validator for Rails

Add subdomain_validation gem to your Gemfile.

gem 'subdomain_validation'

Run bundler.

bundle install

First, Add SubdomainValidation module to a model.

class User < ActiveRecord::Base
  include SubdomainValidation
end

Next, add validates method on a column in the model.

class User < ActiveRecord::Base
  include SubdomainValidation

  validates :username, subdomain: true
end

• Be not nil.
  • Allow by using allow_nil option
• Be not blank.
  • Allow by using allow_blank option
• Be not reserved name.
  • Customize by using reserved_name option
• Be more than 3 characters.
• Be less than or equal to 63 characters.
• Be in alphanumeric and hyphen.
• Do not start hyphen.
• Do not end hyphen.

RFC 1035 - Domain names - implementation and specification

• reserved_name
  • The following name are prohibited to register by default. You can customize thease name.
    • www
    • http
    • https
    • ftp
    • sftp
    • ssl
    • ns
    • mx
    • pop
    • smtp
    • admin
    • mail
    • users

• reserved_name
  • Values: String Array or False
  • String Array
    • You can reserve the words which can not be taken.
    • If use this option, then default reserved_name will be disabled.
    • validates :username, subdomain: { reserved_name: %w(www blog admin) }
  • False
    • You can disable reserved_name feature.
    • If use this option, then default reserved_name will be disabled.
    • validates :username, subdomain: { reserved_name: false }
• Common options
  • allow_nil
    • You can allow nil value by using allow_nil option.
    • validates :username, subdomain: true, allow_nil: true
  • allow_blank
    • You can allow blank value by using allow_blank option.
    • validates :username, subdomain: true, allow_blank: true
  • on
    • You can specify when the validation should happen.
    • validates :username, subdomain: true, on: :create

You can customize or add validation error messages. Add following keys to your locale file in config/locales.

en:
  subdomain_validation:
    errors:
      messages:
        label:           "can only include letters and numbers and \"-\""
        first_character: "can't start with \"-\""
        last_character:  "can't end with \"-\""

Or, make a pull request :)

This project rocks and uses MIT-LICENSE.