ActiveRecord and ActionPack now use the new descendants implementation.

actionpack/lib/abstract_controller/base.rb

@@ -1,4 +1,5 @@
 require 'active_support/configurable'
+require 'active_support/descendants_tracker'
 require 'active_support/core_ext/module/anonymous'
 
 module AbstractController
@@ -10,6 +11,7 @@ module AbstractController
     attr_internal :action_name
 
     include ActiveSupport::Configurable
+    extend ActiveSupport::DescendantsTracker
 
     class << self
       attr_reader :abstract
@@ -21,17 +23,6 @@ module AbstractController
         @abstract = true
       end
 
-      def inherited(klass)
-        ::AbstractController::Base.descendants << klass.to_s
-        super
-      end
-
-      # A list of all descendents of AbstractController::Base. This is
-      # useful for initializers which need to add behavior to all controllers.
-      def descendants
-        @descendants ||= []
-      end
-
       # A list of all internal methods for a controller. This finds the first
       # abstract superclass of a controller, and gets a list of all public
       # instance methods on that abstract class. Public instance methods of

activerecord/lib/active_record/associations.rb

@@ -2066,7 +2066,7 @@ module ActiveRecord
               unless klass.descends_from_active_record?
                 sti_column = aliased_table[klass.inheritance_column]
                 sti_condition = sti_column.eq(klass.sti_name)
-                klass.send(:subclasses).each {|subclass| sti_condition = sti_condition.or(sti_column.eq(subclass.sti_name)) }
+                klass.descendants.each {|subclass| sti_condition = sti_condition.or(sti_column.eq(subclass.sti_name)) }
 
                 @join << sti_condition
               end

activerecord/lib/active_record/base.rb

@@ -2,6 +2,7 @@ require 'yaml'
 require 'set'
 require 'active_support/benchmarkable'
 require 'active_support/dependencies'
+require 'active_support/descendants_tracker'
 require 'active_support/time'
 require 'active_support/core_ext/class/attribute'
 require 'active_support/core_ext/class/attribute_accessors'
@@ -274,28 +275,6 @@ module ActiveRecord #:nodoc:
     # on to any new database connections made and which can be retrieved on both a class and instance level by calling +logger+.
     cattr_accessor :logger, :instance_writer => false
 
-    def self.inherited(child) #:nodoc:
-      @@subclasses[self] ||= []
-      @@subclasses[self] << child
-      super
-    end
-
-    def self.reset_subclasses #:nodoc:
-      nonreloadables = []
-      subclasses.each do |klass|
-        unless ActiveSupport::Dependencies.autoloaded? klass
-          nonreloadables << klass
-          next
-        end
-        klass.instance_variables.each { |var| klass.send(:remove_instance_variable, var) }
-        klass.instance_methods(false).each { |m| klass.send :undef_method, m }
-      end
-      @@subclasses = {}
-      nonreloadables.each { |klass| (@@subclasses[klass.superclass] ||= []) << klass }
-    end
-
-    @@subclasses = {}
-
     ##
     # :singleton-method:
     # Contains the database configuration - as is typically stored in config/database.yml -
@@ -810,7 +789,7 @@ module ActiveRecord #:nodoc:
       end
 
       def reset_column_information_and_inheritable_attributes_for_all_subclasses#:nodoc:
-        subclasses.each { |klass| klass.reset_inheritable_attributes; klass.reset_column_information }
+        descendants.each { |klass| klass.reset_inheritable_attributes; klass.reset_column_information }
       end
 
       def attribute_method?(attribute)
@@ -975,7 +954,7 @@ module ActiveRecord #:nodoc:
         def type_condition
           sti_column = arel_table[inheritance_column]
           condition = sti_column.eq(sti_name)
-          subclasses.each{|subclass| condition = condition.or(sti_column.eq(subclass.sti_name)) }
+          descendants.each { |subclass| condition = condition.or(sti_column.eq(subclass.sti_name)) }
 
           condition
         end
@@ -1165,14 +1144,6 @@ module ActiveRecord #:nodoc:
           with_scope(method_scoping, :overwrite, &block)
         end
 
-        # Returns a list of all subclasses of this class, meaning all descendants.
-        def subclasses
-          @@subclasses[self] ||= []
-          @@subclasses[self] + @@subclasses[self].inject([]) {|list, subclass| list + subclass.subclasses }
-        end
-
-        public :subclasses
-
         # Sets the default options for the model. The format of the
         # <tt>options</tt> argument is the same as in find.
         #
@@ -1900,6 +1871,7 @@ module ActiveRecord #:nodoc:
     extend ActiveModel::Naming
     extend QueryCache::ClassMethods
     extend ActiveSupport::Benchmarkable
+    extend ActiveSupport::DescendantsTracker
 
     include ActiveModel::Conversion
     include Validations

activerecord/lib/active_record/observer.rb

@@ -105,8 +105,9 @@ module ActiveRecord
     end
 
     protected
+
       def observed_subclasses
-        observed_classes.sum([]) { |klass| klass.send(:subclasses) }
+        observed_classes.sum([]) { |klass| klass.send(:descendants) }
       end
 
       def observe_callbacks?

activerecord/test/cases/base_test.rb

@@ -2076,10 +2076,6 @@ class BasicsTest < ActiveRecord::TestCase
     assert !SubStiPost.descends_from_active_record?
   end
 
-  def test_base_subclasses_is_public_method
-    assert ActiveRecord::Base.public_methods.map(&:to_sym).include?(:subclasses)
-  end
-
   def test_find_on_abstract_base_class_doesnt_use_type_condition
     old_class = LooseDescendant
     Object.send :remove_const, :LooseDescendant