3 files changed, 49 insertions, 21 deletions
diff --git a/activemodel/lib/active_model/naming.rb b/activemodel/lib/active_model/naming.rb
index f16459ede2..2566920d63 100644
--- a/activemodel/lib/active_model/naming.rb
+++ b/activemodel/lib/active_model/naming.rb
@@ -13,18 +13,18 @@ module ActiveModel
     def initialize(klass, namespace = nil, name = nil)
       name ||= klass.name
       super(name)
-      @unnamespaced = self.sub(/^#{namespace.name}::/, '') if namespace
 
-      @klass = klass
-      @singular = _singularize(self).freeze
-      @plural = ActiveSupport::Inflector.pluralize(@singular).freeze
-      @element = ActiveSupport::Inflector.underscore(ActiveSupport::Inflector.demodulize(self)).freeze
-      @human = ActiveSupport::Inflector.humanize(@element).freeze
-      @collection = ActiveSupport::Inflector.tableize(self).freeze
+      @unnamespaced = self.sub(/^#{namespace.name}::/, '') if namespace
+      @klass        = klass
+      @singular     = _singularize(self).freeze
+      @plural       = ActiveSupport::Inflector.pluralize(@singular).freeze
+      @element      = ActiveSupport::Inflector.underscore(ActiveSupport::Inflector.demodulize(self)).freeze
+      @human        = ActiveSupport::Inflector.humanize(@element).freeze
+      @collection   = ActiveSupport::Inflector.tableize(self).freeze
       @partial_path = "#{@collection}/#{@element}".freeze
-      @param_key = (namespace ? _singularize(@unnamespaced) : @singular).freeze
-      @route_key = (namespace ? ActiveSupport::Inflector.pluralize(@param_key) : @plural).freeze
-      @i18n_key = self.underscore.to_sym
+      @param_key    = (namespace ? _singularize(@unnamespaced) : @singular).freeze
+      @route_key    = (namespace ? ActiveSupport::Inflector.pluralize(@param_key) : @plural).freeze
+      @i18n_key     = self.underscore.to_sym
     end
 
     # Transform the model name into a more humane format, using I18n. By default,
@@ -79,7 +79,9 @@ module ActiveModel
     # used to retrieve all kinds of naming-related information.
     def model_name
       @_model_name ||= begin
-        namespace = self.parents.detect { |n| n.respond_to?(:_railtie) }
+        namespace = self.parents.detect do |n|
+          n.respond_to?(:use_relative_model_naming?) && n.use_relative_model_naming?
+        end
         ActiveModel::Name.new(self, namespace)
       end
     end
diff --git a/activemodel/test/cases/naming_test.rb b/activemodel/test/cases/naming_test.rb
index 5f943729dd..a5ee2d6090 100644
--- a/activemodel/test/cases/naming_test.rb
+++ b/activemodel/test/cases/naming_test.rb
@@ -74,10 +74,6 @@ class NamingWithNamespacedModelInIsolatedNamespaceTest < ActiveModel::TestCase
   def test_param_key
     assert_equal 'post', @model_name.param_key
   end
-
-  def test_recognizing_namespace
-    assert_equal 'Post', Blog::Post.model_name.instance_variable_get("@unnamespaced")
-  end
 end
 
 class NamingWithNamespacedModelInSharedNamespaceTest < ActiveModel::TestCase
@@ -160,6 +156,40 @@ class NamingWithSuppliedModelNameTest < ActiveModel::TestCase
   end
 end
 
+class NamingUsingRelativeModelNameTest < ActiveModel::TestCase
+  def setup
+    @model_name = Blog::Post.model_name
+  end
+
+  def test_singular
+    assert_equal 'blog_post', @model_name.singular
+  end
+
+  def test_plural
+    assert_equal 'blog_posts', @model_name.plural
+  end
+
+  def test_element
+    assert_equal 'post', @model_name.element
+  end
+
+  def test_collection
+    assert_equal 'blog/posts', @model_name.collection
+  end
+
+  def test_human
+    assert_equal 'Post', @model_name.human
+  end
+
+  def test_route_key
+    assert_equal 'posts', @model_name.route_key
+  end
+
+  def test_param_key
+    assert_equal 'post', @model_name.param_key
+  end
+end
+
 class NamingHelpersTest < Test::Unit::TestCase
   def setup
     @klass  = Contact
diff --git a/activemodel/test/models/blog_post.rb b/activemodel/test/models/blog_post.rb
index d289177259..46eba857df 100644
--- a/activemodel/test/models/blog_post.rb
+++ b/activemodel/test/models/blog_post.rb
@@ -1,10 +1,6 @@
 module Blog
-  def self._railtie
-    Object.new
-  end
-
-  def self.table_name_prefix
-    "blog_"
+  def self.use_relative_model_naming?
+    true
   end
 
   class Post