Added Object#metaclass

activesupport/lib/active_support/core_ext/object.rb

 require 'active_support/core_ext/object/conversions'
 require 'active_support/core_ext/object/extending'
 require 'active_support/core_ext/object/instance_variables'
+require 'active_support/core_ext/object/metaclass'
 require 'active_support/core_ext/object/misc'

activesupport/lib/active_support/core_ext/object/metaclass.rb

+class Object
+  # Get object's meta (ghost, eigenclass, singleton) class
+  def metaclass
+    class << self
+      self
+    end
+  end
+end

activesupport/test/core_ext/object_and_class_ext_test.rb

@@ -173,6 +173,14 @@ def test_duck_typing
     assert duck.acts_like?(:time)
     assert !duck.acts_like?(:date)
   end
+
+  def test_metaclass
+    string = "Hello"
+    string.metaclass.instance_eval do
+      define_method(:foo) { "bar" }
+    end
+    assert_equal "bar", string.foo
+  end
 end
 
 class ObjectInstanceVariableTest < Test::Unit::TestCase