14 files changed, 44 insertions, 35 deletions
diff --git a/actionpack/lib/action_dispatch/testing/integration.rb b/actionpack/lib/action_dispatch/testing/integration.rb
index f93059759b..14c7ff642b 100644
--- a/actionpack/lib/action_dispatch/testing/integration.rb
+++ b/actionpack/lib/action_dispatch/testing/integration.rb
@@ -1,6 +1,6 @@
 require 'stringio'
 require 'uri'
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 require 'rack/test'
 
 module ActionDispatch
@@ -187,7 +187,7 @@ module ActionDispatch
 
         unless defined? @named_routes_configured
           # install the named routes in this session instance.
-          klass = metaclass
+          klass = singleton_class
           ActionDispatch::Routing::Routes.install_helpers(klass)
 
           # the helpers are made protected by default--we make them public for
diff --git a/activemodel/lib/active_model/attribute_methods.rb b/activemodel/lib/active_model/attribute_methods.rb
index 200a6afbf0..143eb87f54 100644
--- a/activemodel/lib/active_model/attribute_methods.rb
+++ b/activemodel/lib/active_model/attribute_methods.rb
@@ -86,7 +86,7 @@ module ActiveModel
       #   AttributePerson.inheritance_column
       #   # => 'address_id'
       def define_attr_method(name, value=nil, &block)
-        sing = metaclass
+        sing = singleton_class
         sing.send :alias_method, "original_#{name}", name
         if block_given?
           sing.send :define_method, name, &block
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index ef5a7d5787..83f0b58e8a 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -11,7 +11,7 @@ require 'active_support/core_ext/hash/deep_merge'
 require 'active_support/core_ext/hash/indifferent_access'
 require 'active_support/core_ext/hash/slice'
 require 'active_support/core_ext/string/behavior'
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 require 'active_support/core_ext/module/delegation'
 
 module ActiveRecord #:nodoc:
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 068d2a25b2..fd5ffc6d77 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -1,4 +1,4 @@
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 
 module ActiveRecord
   # Exception that can be raised to stop migrations from going backwards.
@@ -303,7 +303,7 @@ module ActiveRecord
 
           case sym
             when :up, :down
-              metaclass.send(:alias_method_chain, sym, "benchmarks")
+              singleton_class.send(:alias_method_chain, sym, "benchmarks")
           end
         ensure
           @ignore_new_methods = false
diff --git a/activerecord/lib/active_record/named_scope.rb b/activerecord/lib/active_record/named_scope.rb
index ff6c041ef4..f1f56850ae 100644
--- a/activerecord/lib/active_record/named_scope.rb
+++ b/activerecord/lib/active_record/named_scope.rb
@@ -1,6 +1,6 @@
 require 'active_support/core_ext/array'
 require 'active_support/core_ext/hash/except'
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 
 module ActiveRecord
   module NamedScope
@@ -112,7 +112,7 @@ module ActiveRecord
               options.call(*args)
           end, &block)
         end
-        metaclass.instance_eval do
+        singleton_class.instance_eval do
           define_method name do |*args|
             scopes[name].call(self, *args)
           end
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 8ec903e376..56c81cf63b 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *Rails 3.0 (pending)*
 
+* Use Object#singleton_class instead of #metaclass. Prefer Ruby's choice.  [Jeremy Kemper]
+
 * JSON backend for YAJL. Preferred if available.  #2666 [Brian Lopez]
 
 
diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index 6727eda811..b230bb8a40 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -1,7 +1,7 @@
 require 'active_support/core_ext/array/wrap'
 require 'active_support/core_ext/class/inheritable_attributes'
 require 'active_support/core_ext/kernel/reporting'
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 
 module ActiveSupport
   # Callbacks are hooks into the lifecycle of an object that allow you to trigger logic
@@ -312,7 +312,7 @@ module ActiveSupport
 
       def _normalize_legacy_filter(kind, filter)
         if !filter.respond_to?(kind) && filter.respond_to?(:filter)
-          filter.metaclass.class_eval(
+          filter.singleton_class.class_eval(
             "def #{kind}(context, &block) filter(context, &block) end",
             __FILE__, __LINE__ - 1)
         elsif filter.respond_to?(:before) && filter.respond_to?(:after) && kind == :around
diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb
index d74219cb93..1bd39a9349 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute.rb
@@ -1,4 +1,4 @@
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 require 'active_support/core_ext/module/delegation'
 
 class Class
@@ -25,11 +25,12 @@ class Class
   #
   #   Subclass.setting?           # => false
   def class_attribute(*attrs)
+    s = singleton_class
     attrs.each do |attr|
-      metaclass.send(:define_method, attr) { }
-      metaclass.send(:define_method, "#{attr}?") { !!send(attr) }
-      metaclass.send(:define_method, "#{attr}=") do |value|
-        metaclass.send(:define_method, attr) { value }
+      s.send(:define_method, attr) { }
+      s.send(:define_method, "#{attr}?") { !!send(attr) }
+      s.send(:define_method, "#{attr}=") do |value|
+        singleton_class.send(:define_method, attr) { value }
       end
     end
   end
diff --git a/activesupport/lib/active_support/core_ext/class/delegating_attributes.rb b/activesupport/lib/active_support/core_ext/class/delegating_attributes.rb
index 19382abb76..b5785bdcd3 100644
--- a/activesupport/lib/active_support/core_ext/class/delegating_attributes.rb
+++ b/activesupport/lib/active_support/core_ext/class/delegating_attributes.rb
@@ -1,6 +1,6 @@
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/array/extract_options'
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 
 class Class
   def superclass_delegating_accessor(name, options = {})
@@ -11,9 +11,9 @@ class Class
     # Generate the public methods name, name=, and name?
     # These methods dispatch to the private _name, and _name= methods, making them
     # overridable
-    metaclass.send(:define_method, name) { send("_#{name}") }
-    metaclass.send(:define_method, "#{name}?") { !!send("_#{name}") }
-    metaclass.send(:define_method, "#{name}=") { |value| send("_#{name}=", value) }
+    singleton_class.send(:define_method, name) { send("_#{name}") }
+    singleton_class.send(:define_method, "#{name}?") { !!send("_#{name}") }
+    singleton_class.send(:define_method, "#{name}=") { |value| send("_#{name}=", value) }
 
     # If an instance_reader is needed, generate methods for name and name= on the
     # class itself, so instances will be able to see them
@@ -27,12 +27,12 @@ private
   # inheritance behavior, without having to store the object in an instance
   # variable and look up the superclass chain manually.
   def _stash_object_in_method(object, method, instance_reader = true)
-    metaclass.send(:define_method, method) { object }
+    singleton_class.send(:define_method, method) { object }
     define_method(method) { object } if instance_reader
   end
 
   def _superclass_delegating_accessor(name, options = {})
-    metaclass.send(:define_method, "#{name}=") do |value|
+    singleton_class.send(:define_method, "#{name}=") do |value|
       _stash_object_in_method(value, name, options[:instance_reader] != false)
     end
     self.send("#{name}=", nil)
diff --git a/activesupport/lib/active_support/core_ext/object.rb b/activesupport/lib/active_support/core_ext/object.rb
index db2dac1472..9dc6ca66a4 100644
--- a/activesupport/lib/active_support/core_ext/object.rb
+++ b/activesupport/lib/active_support/core_ext/object.rb
@@ -6,6 +6,7 @@ require 'active_support/core_ext/object/try'
 require 'active_support/core_ext/object/conversions'
 require 'active_support/core_ext/object/instance_variables'
 require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 require 'active_support/core_ext/object/misc'
 require 'active_support/core_ext/object/extending'
 
diff --git a/activesupport/lib/active_support/core_ext/object/metaclass.rb b/activesupport/lib/active_support/core_ext/object/metaclass.rb
index 93fb0ad594..4b36a243c9 100644
--- a/activesupport/lib/active_support/core_ext/object/metaclass.rb
+++ b/activesupport/lib/active_support/core_ext/object/metaclass.rb
@@ -1,13 +1,14 @@
+require 'active_support/deprecation'
+
 class Object
-  # Get object's meta (ghost, eigenclass, singleton) class
+  # Get object's meta (ghost, eigenclass, singleton) class.
+  #
+  # Deprecated in favor of Object#singleton_class.
   def metaclass
     class << self
       self
     end
   end
 
-  # If class_eval is called on an object, add those methods to its metaclass
-  def class_eval(*args, &block)
-    metaclass.class_eval(*args, &block)
-  end
+  deprecate :metaclass => :singleton_class
 end
diff --git a/activesupport/lib/active_support/memoizable.rb b/activesupport/lib/active_support/memoizable.rb
index f810f53029..ca1cfedae3 100644
--- a/activesupport/lib/active_support/memoizable.rb
+++ b/activesupport/lib/active_support/memoizable.rb
@@ -1,4 +1,4 @@
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 require 'active_support/core_ext/module/aliasing'
 
 module ActiveSupport
diff --git a/activesupport/test/core_ext/object_and_class_ext_test.rb b/activesupport/test/core_ext/object_and_class_ext_test.rb
index f31e7774e9..00c59d84b8 100644
--- a/activesupport/test/core_ext/object_and_class_ext_test.rb
+++ b/activesupport/test/core_ext/object_and_class_ext_test.rb
@@ -89,7 +89,7 @@ class ClassExtTest < Test::Unit::TestCase
   end
 end
 
-class ObjectTests < Test::Unit::TestCase
+class ObjectTests < ActiveSupport::TestCase
   class DuckTime
     def acts_like_time?
       true
@@ -119,12 +119,16 @@ class ObjectTests < Test::Unit::TestCase
     assert !duck.acts_like?(:date)
   end
 
-  def test_metaclass
-    string = "Hello"
-    string.metaclass.instance_eval do
-      define_method(:foo) { "bar" }
+  def test_singleton_class
+    o = Object.new
+    assert_equal class << o; self end, o.singleton_class
+  end
+
+  def test_metaclass_deprecated
+    o = Object.new
+    assert_deprecated /use singleton_class instead/ do
+      assert_equal o.singleton_class, o.metaclass
     end
-    assert_equal "bar", string.foo
   end
 end
 
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index c01018aab2..f24dc620de 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -3,7 +3,7 @@ $:.unshift(activesupport_path) if File.directory?(activesupport_path) && !$:.inc
 
 require 'active_support'
 require 'active_support/core_ext/object/blank'
-require 'active_support/core_ext/object/metaclass'
+require 'active_support/core_ext/object/singleton_class'
 require 'active_support/core_ext/array/extract_options'
 require 'active_support/core_ext/hash/deep_merge'
 require 'active_support/core_ext/module/attribute_accessors'
@@ -291,4 +291,4 @@ end
 
 # If the application was already defined, configure generators,
 # otherwise you have to configure it by hand.
-Rails::Generators.configure! if Rails.respond_to?(:application) && Rails.application
-\ No newline at end of file
+Rails::Generators.configure! if Rails.respond_to?(:application) && Rails.application