attr_encrypted supporting different classes Based on http://stackoverflow.com/questions/17482507/correct-way-to-handle-multiparameter-attributes-corresponding-to-virtual-attribu

encrypted_attribute_helper.rb

if defined?(ActiveRecord::Base)
  module AttrEncrypted
    module Adapters
      module ActiveRecord

        protected
        class EncryptedAttributeClassWrapper
          attr_reader :klass
          def initialize(klass); @klass = klass; end
        end

        def encrypted_attribute_class_wrappers
          @encrypted_attribute_class_wrappers ||= {}
        end

        alias_method :attr_encrypted_base, :attr_encrypted
        def attr_encrypted(*args)
          options = args.last.is_a?(Hash) ? args.pop : {}

          if klass = options.delete(:class)
            attribute_sym = args.first.to_sym
            self.encrypted_attribute_class_wrappers[attribute_sym] = EncryptedAttributeClassWrapper.new(klass)
          end

          new_args = args + [options]
          attr_encrypted_base *new_args
        end

      end
    end
  end
  class ActiveRecord::Base
    protected
    alias_method :column_for_attribute_base, :column_for_attribute
    def column_for_attribute(attribute)
      attribute_sym = attribute.to_sym
      if encrypted = self.class.encrypted_attributes[attribute_sym]
        column_info = self.class.send(:encrypted_attribute_class_wrappers)[attribute_sym]
        column_info ||= column_for_attribute_base(encrypted[:attribute])
        column_info
      else
        column_for_attribute_base(attribute)
      end
    end
  end
end