Refactor how to get singleton class

lib/utusemi.rb

@@ -15,7 +15,7 @@ def enable
         # for model and relation
         this.prepend_to_activerecord_base
         this.prepend_to_activerecord_relation
-        this.prepend_to_activerecord_eigenclass
+        this.prepend_to_activerecord_singleton_class
         this.prepend_to_activerecord_associations_hasmanyassociation
         this.prepend_to_activerecord_associations_collectionproxy
       end
@@ -43,12 +43,12 @@ def prepend_to_activerecord_relation
       ActiveRecord::Relation.send(:prepend, Core::ActiveRecord::Relation)
     end
 
-    def prepend_to_activerecord_eigenclass
-      activerecord_eigenclass.send(:prepend, Core::ActiveRecord::Base::ClassMethods)
+    def prepend_to_activerecord_singleton_class
+      ActiveRecord::Base.singleton_class.send(:prepend, Core::ActiveRecord::Base::ClassMethods)
       # for rails 3.x
-      activerecord_eigenclass.send(:prepend, Core::ActiveRecord::RelationMethod) if Rails::VERSION::MAJOR == 3
+      ActiveRecord::Base.singleton_class.send(:prepend, Core::ActiveRecord::RelationMethod) if Rails::VERSION::MAJOR == 3
       # for association
-      activerecord_eigenclass.send(:prepend, Core::ActiveRecord::AssociationMethods)
+      ActiveRecord::Base.singleton_class.send(:prepend, Core::ActiveRecord::AssociationMethods)
     end
 
     def prepend_to_activerecord_associations_hasmanyassociation
@@ -58,11 +58,5 @@ def prepend_to_activerecord_associations_hasmanyassociation
     def prepend_to_activerecord_associations_collectionproxy
       ActiveRecord::Associations::CollectionProxy.send(:prepend, Core::ActiveRecord::CollectionProxy) if Rails::VERSION::MAJOR == 3
     end
-
-    private
-
-    def activerecord_eigenclass
-      ActiveRecord::Base.class_eval { class << self; self; end }
-    end
   end
 end

lib/utusemi/core.rb

@@ -309,8 +309,7 @@ def initialize_copy(original_obj)
         def association(name)
           truthly_owner = self
           association = super
-          eigenclass = class << association; self; end
-          eigenclass.send(:define_method, :truthly_owner) { truthly_owner }
+          association.singleton_class.send(:define_method, :truthly_owner) { truthly_owner }
           association
         end
       end