From bca5499e912b12e8c87214ad08ead88b9ecef992 Mon Sep 17 00:00:00 2001
From: Nobuhiro IMAI <nov@yo.rim.or.jp>
Date: Fri, 23 Oct 2009 18:46:27 +0900
Subject: [PATCH 1/2] [nested attributes]: use existing record on one to one association

---
 .../lib/active_record/nested_attributes.rb         |    8 +++-
 activerecord/test/cases/nested_attributes_test.rb  |   34 ++++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index edcf547..d69f375 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -223,7 +223,7 @@ module ActiveRecord
       def accepts_nested_attributes_for(*attr_names)
         options = { :allow_destroy => false }
         options.update(attr_names.extract_options!)
-        options.assert_valid_keys(:allow_destroy, :reject_if, :limit)
+        options.assert_valid_keys(:allow_destroy, :reject_if, :limit, :use_existing_record)
 
         attr_names.each do |association_name|
           if reflection = reflect_on_association(association_name)
@@ -295,6 +295,10 @@ module ActiveRecord
       options = self.nested_attributes_options[association_name]
       attributes = attributes.with_indifferent_access
 
+      if options[:use_existing_record] and attributes['id'].blank?
+        existing_record = __send__(association_name)
+        attributes['id'] = existing_record.id if existing_record
+      end
       if attributes['id'].blank?
         unless reject_new_record?(association_name, attributes)
           method = "build_#{association_name}"
@@ -304,7 +308,7 @@ module ActiveRecord
             raise ArgumentError, "Cannot build association #{association_name}. Are you trying to build a polymorphic one-to-one association?"
           end
         end
-      elsif (existing_record = send(association_name)) && existing_record.id.to_s == attributes['id'].to_s
+      elsif (existing_record ||= send(association_name)) && existing_record.id.to_s == attributes['id'].to_s
         assign_to_or_mark_for_destruction(existing_record, attributes, options[:allow_destroy])
       end
     end
diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index 53fd168..74ada18 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -245,6 +245,23 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_automatically_enable_autosave_on_the_association
     assert Pirate.reflect_on_association(:ship).options[:autosave]
   end
+
+  def test_should_update_existing_record_if_specified
+    Pirate.accepts_nested_attributes_for :ship, :use_existing_record => true
+
+    ship_id = @ship.id
+    assert_no_difference('Ship.count') do
+      @pirate.update_attributes!(:ship_attributes => {:name => 'Thousand Sunny'})
+    end
+    assert_equal 'Thousand Sunny', Ship.find(ship_id).name
+    @ship.destroy
+    @pirate.reload.ship_attributes = {:name => 'Big Top'}
+    assert_equal true, @pirate.ship.new_record?, "should be built now"
+    assert_difference('Ship.count') do
+      @pirate.save!
+    end
+    assert_equal 'Big Top', @pirate.ship(true).name
+  end
 end
 
 class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
@@ -362,6 +379,23 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
   def test_should_automatically_enable_autosave_on_the_association
     assert Ship.reflect_on_association(:pirate).options[:autosave]
   end
+
+  def test_should_update_existing_record_if_specified
+    Ship.accepts_nested_attributes_for :pirate, :use_existing_record => true
+
+    pirate_id = @pirate.id
+    assert_no_difference('Pirate.count') do
+      @ship.update_attributes!(:pirate_attributes => {:catchphrase => 'from a spoon'})
+    end
+    assert_equal 'from a spoon', Pirate.find(pirate_id).catchphrase
+    @pirate.destroy
+    @ship.reload.pirate_attributes = {:catchphrase => 'to Space Battleship'}
+    assert_equal true, @ship.pirate.new_record?, "should be built now"
+    assert_difference('Pirate.count') do
+      @ship.save!
+    end
+    assert_equal 'to Space Battleship', @ship.pirate(true).catchphrase
+  end
 end
 
 module NestedAttributesOnACollectionAssociationTests
-- 
1.6.5