Merge commit 'mainstream/master'

Conflicts:
	railties/guides/files/javascripts/code_highlighter.js
	railties/guides/files/javascripts/guides.js
	railties/guides/files/javascripts/highlighters.js
	railties/guides/files/stylesheets/main.css
	railties/guides/files/stylesheets/print.css
	railties/guides/files/stylesheets/reset.css
	railties/guides/files/stylesheets/style.css
	railties/guides/files/stylesheets/syntax.css
	railties/guides/rails_guides/indexer.rb
	railties/guides/source/2_2_release_notes.textile
	railties/guides/source/2_3_release_notes.textile
	railties/guides/source/action_controller_overview.textile
	railties/guides/source/action_mailer_basics.textile
	railties/guides/source/active_record_basics.textile
	railties/guides/source/activerecord_validations_callbacks.textile
	railties/guides/source/association_basics.textile
	railties/guides/source/caching_with_rails.textile
	railties/guides/source/command_line.textile
	railties/guides/source/debugging_rails_applications.textile
	railties/guides/source/form_helpers.textile
	railties/guides/source/getting_started.textile
	railties/guides/source/i18n.textile
	railties/guides/source/layout.html.erb
	railties/guides/source/layouts_and_rendering.textile
	railties/guides/source/migrations.textile
	railties/guides/source/performance_testing.textile
	railties/guides/source/plugins.textile
	railties/guides/source/rails_on_rack.textile
	railties/guides/source/routing.textile
	railties/guides/source/security.textile
	railties/guides/source/testing.textile

1 files changed, 6 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index 8bfdadd0e3..5778223c74 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -86,7 +86,8 @@ module ActiveRecord
     # For each key in the hash that starts with the string 'new' a new model
     # will be instantiated. When the proc given with the <tt>:reject_if</tt>
     # option evaluates to +false+ for a certain attribute hash no record will
-    # be built for that hash.
+    # be built for that hash. (Rejecting new records can alternatively be done
+    # by utilizing the <tt>'_delete'</tt> key. Scroll down for more info.)
     #
     #   params = { 'member' => {
     #     'name' => 'joe', 'posts_attributes' => {
@@ -258,11 +259,14 @@ module ActiveRecord
     # If a <tt>:reject_if</tt> proc exists for this association, it will be
     # called with the attributes as its argument. If the proc returns a truthy
     # value, the record is _not_ build.
+    #
+    # Alternatively, you can specify the <tt>'_delete'</tt> key to _not_ build
+    # a record. See should_destroy_nested_attributes_record? for more info.
     def build_new_nested_attributes_record(association_name, attributes)
       if reject_proc = self.class.reject_new_nested_attributes_procs[association_name]
         return if reject_proc.call(attributes)
       end
-      send(association_name).build(attributes)
+      send(association_name).build(attributes) unless should_destroy_nested_attributes_record?(true, attributes)
     end
 
     # Assigns the attributes to the record specified by +id+. Or marks it for