Use #model_name on instances instead of classes

This allows rails code to be more confdent when asking for a model name, instead of having to ask for the class.

Rails core discussion here: https://groups.google.com/forum/#!topic/rubyonrails-core/ThSaXw9y1F8

6 files changed, 12 insertions, 8 deletions

diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index 917d3b9142..95029fd538 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -434,7 +434,7 @@ module ActiveModel
 
       options = {
         default: defaults,
-        model: @base.class.model_name.human,
+        model: @base.model_name.human,
         attribute: @base.class.human_attribute_name(attribute),
         value: value
       }.merge!(options)
diff --git a/activemodel/lib/active_model/lint.rb b/activemodel/lib/active_model/lint.rb
index c6bc18b008..38087521a2 100644
--- a/activemodel/lib/active_model/lint.rb
+++ b/activemodel/lib/active_model/lint.rb
@@ -73,16 +73,19 @@ module ActiveModel
 
       # == \Naming
       #
-      # Model.model_name must return a string with some convenience methods:
-      # <tt>:human</tt>, <tt>:singular</tt> and <tt>:plural</tt>. Check
-      # ActiveModel::Naming for more information.
+      # Model.model_name and Model#model_name must return a string with some
+      # convenience methods: # <tt>:human</tt>, <tt>:singular</tt> and
+      # <tt>:plural</tt>. Check ActiveModel::Naming for more information.
       def test_model_naming
-        assert model.class.respond_to?(:model_name), "The model should respond to model_name"
+        assert model.class.respond_to?(:model_name), "The model class should respond to model_name"
         model_name = model.class.model_name
         assert model_name.respond_to?(:to_str)
         assert model_name.human.respond_to?(:to_str)
         assert model_name.singular.respond_to?(:to_str)
         assert model_name.plural.respond_to?(:to_str)
+
+        assert model.respond_to?(:model_name), "The model instance should respond to model_name"
+        assert_equal model.model_name, model.class.model_name
       end
 
       # == \Errors Testing
diff --git a/activemodel/lib/active_model/naming.rb b/activemodel/lib/active_model/naming.rb
index 8cf1a191f4..ef3449b7cb 100644
--- a/activemodel/lib/active_model/naming.rb
+++ b/activemodel/lib/active_model/naming.rb
@@ -308,7 +308,7 @@ module ActiveModel
       if record_or_class.respond_to?(:model_name)
         record_or_class.model_name
       elsif record_or_class.respond_to?(:to_model)
-        record_or_class.to_model.class.model_name
+        record_or_class.to_model.model_name
       else
         record_or_class.class.model_name
       end
diff --git a/activemodel/lib/active_model/serializers/json.rb b/activemodel/lib/active_model/serializers/json.rb
index c58e73f6a7..77f2a64b11 100644
--- a/activemodel/lib/active_model/serializers/json.rb
+++ b/activemodel/lib/active_model/serializers/json.rb
@@ -93,7 +93,7 @@ module ActiveModel
         end
 
         if root
-          root = self.class.model_name.element if root == true
+          root = model_name.element if root == true
           { root => serializable_hash(options) }
         else
           serializable_hash(options)
diff --git a/activemodel/lib/active_model/serializers/xml.rb b/activemodel/lib/active_model/serializers/xml.rb
index 7f99536dbb..3ad3bf30ad 100644
--- a/activemodel/lib/active_model/serializers/xml.rb
+++ b/activemodel/lib/active_model/serializers/xml.rb
@@ -84,7 +84,7 @@ module ActiveModel
           @builder = options[:builder]
           @builder.instruct! unless options[:skip_instruct]
 
-          root = (options[:root] || @serializable.class.model_name.element).to_s
+          root = (options[:root] || @serializable.model_name.element).to_s
           root = ActiveSupport::XmlMini.rename_key(root, options)
 
           args = [root]
diff --git a/activemodel/lib/active_model/validations.rb b/activemodel/lib/active_model/validations.rb
index cf97f45dba..e546863305 100644
--- a/activemodel/lib/active_model/validations.rb
+++ b/activemodel/lib/active_model/validations.rb
@@ -39,6 +39,7 @@ module ActiveModel
     extend ActiveSupport::Concern
 
     included do
+      extend ActiveModel::Naming
       extend ActiveModel::Callbacks
       extend ActiveModel::Translation