Add ActiveRecord::attribute_names to retrieve a list of attribute names. This...

Add ActiveRecord::attribute_names to retrieve a list of attribute names. This method will also return an empty array on an abstract class or a model that the table doesn't exists.

activerecord/CHANGELOG

 *Rails 3.1.0 (unreleased)*
 
+* Add ActiveRecord::Base.attribute_names to return a list of attribute names. This will return an empty array if the model is abstract or table does not exists. [Prem Sichanugrist]
+
 * CSV Fixtures are deprecated and support will be removed in Rails 3.2.0
 
 * AR#new, AR#create, AR#create!, AR#update_attributes and AR#update_attributes! all accept a second hash as option that allows you

activerecord/lib/active_record/base.rb

@@ -767,6 +767,14 @@ def attribute_method?(attribute)
         super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, '')))
       end
 
+      def attribute_names
+        @attribute_names ||= if !abstract_class? && table_exists?
+            column_names
+          else
+            []
+          end
+      end
+
       # Set the lookup ancestors for ActiveModel.
       def lookup_ancestors #:nodoc:
         klass = self

activerecord/test/cases/base_test.rb

@@ -1790,4 +1790,17 @@ def test_marshal_round_trip
 
     assert_equal expected.attributes, actual.attributes
   end
+
+  def test_attribute_names
+    assert_equal ["id", "type", "ruby_type", "firm_id", "firm_name", "name", "client_of", "rating", "account_id"],
+                 Company.attribute_names
+  end
+
+  def test_attribute_names_on_table_not_exists
+    assert_equal [], NonExistentTable.attribute_names
+  end
+
+  def test_attribtue_names_on_abstract_class
+    assert_equal [], AbstractCompany.attribute_names
+  end
 end