normalizer.rb

# Usually normalization is performed during `before_validation`
# or in a setter. But neither would help with normalization of
# where conditions.
#
# This will add `normalize` to ActiveRecord with support for
# where conditions. For example,
#
#   class User
#     normalize(:email) { email.downcase }
#   end
#   User.create(email: 'foo@BAR') # creates foo@bar
#   User.where(email: 'FOO@bar') # finds foo@bar
#
# In rails 5 it could be easily replaced with AR column type API
module Normalize
  class Wrapper
    def initialize(convertor)
      @convertor = convertor
    end
 
    def dump(value)
      @convertor.call value if value
    end
 
    alias load dump
  end
 
  def normalize(attribute, convertor)
    serialize attribute, Wrapper.new(convertor)
  end
end