Remember the stored attributes in a config attribute.

This allows you to retrieve the list of attributes you've defined.
Usable for e.g. selects in the view, or interators based on the
attributes you wish to store in the serialized column.

activerecord/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   Added a `stored_attributes` hash which contains the attributes stored
+    using ActiveRecord::Store. This allows you to retrieve the list of
+    attributes you've defined.
+
+    *Joost Baaij*
+
 *   `composed_of` was removed. You'll have to write your own accessor
     and mutator methods if you'd like to use value objects to represent some
     portion of your models. So, instead of:

activerecord/lib/active_record/store.rb

+require 'active_support/concern'
 require 'active_support/core_ext/hash/indifferent_access'
 
 module ActiveRecord
@@ -33,9 +34,18 @@ module ActiveRecord
   #   class SuperUser < User
   #     store_accessor :settings, :privileges, :servants
   #   end
+  #
+  # The stored attribute names can be retrieved using +stored_attributes+.
+  #
+  #   User.stored_attributes[:settings] # [:color, :homepage]
   module Store
     extend ActiveSupport::Concern
 
+    included do
+      config_attribute :stored_attributes
+      self.stored_attributes = {}
+    end
+
     module ClassMethods
       def store(store_attribute, options = {})
         serialize store_attribute, IndifferentCoder.new(options[:coder])
@@ -55,6 +65,8 @@ def store_accessor(store_attribute, *keys)
             send(store_attribute)[key]
           end
         end
+
+        self.stored_attributes[store_attribute] = keys.flatten
       end
     end
 

activerecord/test/cases/store_test.rb

@@ -13,7 +13,7 @@ class StoreTest < ActiveRecord::TestCase
     assert_equal 'black', @john.color
     assert_nil @john.homepage
   end
-  
+
   test "writing store attributes through accessors" do
     @john.color = 'red'
     @john.homepage = '37signals.com'
@@ -111,4 +111,8 @@ class StoreTest < ActiveRecord::TestCase
     @john.is_a_good_guy = false
     assert_equal false, @john.is_a_good_guy
   end
+
+  test "stored attributes are returned" do
+    assert_equal [:color, :homepage], Admin::User.stored_attributes[:settings]
+  end
 end