Add AssociationCollection#sum since the method_missing invokation has been...

Add AssociationCollection#sum since the method_missing invokation has been shadowed by Enumerable#sum. Closes #5500.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4493 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Add AssociationCollection#sum since the method_missing invokation has been shadowed by Enumerable#sum.
+
 * Added find_or_initialize_by_X which works like find_or_create_by_X but doesn't save the newly instantiated record. [Sam Stephenson]
 
 * Row locking. Provide a locking clause with the :lock finder option or true for the default "FOR UPDATE". Use the #lock! method to obtain a row lock on a single record (reloads the record with :lock => true). [Shugo Maeda]

activerecord/lib/active_record/associations/association_collection.rb

@@ -42,6 +42,11 @@ def delete_all
         reset_target!
       end
 
+      # Calculate sum using SQL, not Enumerable
+      def sum(*args, &block)
+        calculate(:sum, *args, &block)
+      end
+
       # Remove +records+ from this association.  Does not destroy +records+.
       def delete(*records)
         records = flatten_deeper(records)

activerecord/test/calculations_test.rb

@@ -147,6 +147,10 @@ def test_should_calculate_grouped_by_function_with_table_alias
     assert_equal 3, c['CLIENT']
     assert_equal 2, c['FIRM']
   end
+  
+  def test_should_not_overshadow_enumerable_sum
+    assert_equal 6, [1, 2, 3].sum(&:abs)
+  end
 
   def test_should_sum_scoped_field
     assert_equal 15, companies(:rails_core).companies.sum(:id)