Merge pull request #5412 from tilsammans/stored_attributes

Added `stored_attributes` hash which contains the attributes stored using
ActiveRecord::Store. This allows you to retrieve the list of attributes
you've defined.

    class User < ActiveRecord::Base
      store :settings, accessors: [:color, :homepage]
    end

    User.stored_attributes[:settings] # [:color, :homepage]

activerecord/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   Added `stored_attributes` hash which contains the attributes stored using
+    ActiveRecord::Store. This allows you to retrieve the list of attributes
+    you've defined.
+
+       class User < ActiveRecord::Base
+         store :settings, accessors: [:color, :homepage]
+       end
+
+       User.stored_attributes[:settings] # [:color, :homepage]
+
+    *Joost Baaij & Carlos Antonio da Silva*
+
 *   `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'
+require 'active_support/core_ext/class/attribute'
 
 module ActiveRecord
   # Store gives you a thin wrapper around serialize for the purpose of storing hashes in a single column.
@@ -33,9 +35,18 @@ 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
+      class_attribute :stored_attributes
+      self.stored_attributes = {}
+    end
+
     module ClassMethods
       def store(store_attribute, options = {})
         serialize store_attribute, IndifferentCoder.new(options[:coder])
@@ -43,7 +54,8 @@ def store(store_attribute, options = {})
       end
 
       def store_accessor(store_attribute, *keys)
-        keys.flatten.each do |key|
+        keys = keys.flatten
+        keys.each do |key|
           define_method("#{key}=") do |value|
             initialize_store_attribute(store_attribute)
             send(store_attribute)[key] = value
@@ -55,6 +67,8 @@ def store_accessor(store_attribute, *keys)
             send(store_attribute)[key]
           end
         end
+
+        self.stored_attributes[store_attribute] = keys
       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