Rails 3 Email Validator

email_validator.rb

require 'mail'

class EmailValidator < ActiveModel::EachValidator
  attr_reader :record, :attribute, :value, :email, :tree

  def validate_each(record, attribute, value)
    @record, @attribute, @value = record, attribute, value

    @email = Mail::Address.new(value)
    @tree  = email.__send__(:tree)

    add_error unless valid?
  rescue Mail::Field::ParseError
    add_error
  end

  private

  def valid?
    !!(domain_and_address_present? && domain_has_more_than_one_atom?)
  end

  def domain_and_address_present?
    email.domain && email.address == value
  end

  def domain_has_more_than_one_atom?
    tree.domain.dot_atom_text.elements.length > 1
  end

  def add_error
    if message = options[:message]
      record.errors[attribute] << message
    else
      record.errors.add(attribute, :invalid)
    end
  end
end

email_validator_spec.rb

require 'spec_helper'

describe Author do
  def author(attributes = {})
    @author ||= Author.make(attributes) # assuming you're using Machinist
  end

  describe '#email' do
    %w[james@gmail.com man@8.8.8.8 woman@address.tld $@f.c].each do |valid_address|
      context "when #{valid_address.inspect}" do
        it 'has no errors on email' do
          author(email: valid_address).valid?
          author.should have(0).errors_on(:email)
        end
      end
    end

    %w[haxors @blah can@haz].each do |invalid_address|
      context "when #{invalid_address.inspect}" do
        it 'has one error on email' do
          author(email: invalid_address).valid?
          author.should have(1).error_on(:email)
        end
      end
    end
  end
end