Add #delete support to has_many :through associations. Closes #6049 [Martin Landers]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5267 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

3 files changed, 53 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 29c7bfc934..a88b7523a5 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Add #delete support to has_many :through associations.  Closes #6049 [Martin Landers]
+
 * Reverted old select_limited_ids_list postgresql fix that caused issues in mysql.  Closes #5851 [Rick]
 
 * Removes the ability for eager loaded conditions to be interpolated, since there is no model instance to use as a context for interpolation. #5553 [turnip@turnipspatch.com]
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index d7ca7b5834..cbc5616aa8 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -69,6 +69,24 @@ module ActiveRecord
 
       [:push, :concat].each { |method| alias_method method, :<< }
 
+      # Remove +records+ from this association.  Does not destroy +records+.
+      def delete(*records)
+        records = flatten_deeper(records)
+        records.each { |associate| raise_on_type_mismatch(associate) }
+        records.reject! { |associate| @target.delete(associate) if associate.new_record? }
+        return if records.empty?
+        
+        @delete_join_finder ||= "find_all_by_#{@reflection.source_reflection.association_foreign_key}"
+        through = @reflection.through_reflection
+        through.klass.transaction do
+          records.each do |associate|
+            joins = @owner.send(through.name).send(@delete_join_finder, associate.id)
+            @owner.send(through.name).delete(joins)
+            @target.delete(associate)
+          end
+        end
+      end
+
       def build(attrs = nil)
         raise ActiveRecord::HasManyThroughCantAssociateNewRecords.new(@owner, @reflection.through_reflection)
       end
diff --git a/activerecord/test/associations/join_model_test.rb b/activerecord/test/associations/join_model_test.rb
index c67956fba3..7b77765d7a 100644
--- a/activerecord/test/associations/join_model_test.rb
+++ b/activerecord/test/associations/join_model_test.rb
@@ -418,6 +418,39 @@ class AssociationsJoinModelTest < Test::Unit::TestCase
     assert_equal tags, posts(:thinking).tags.push(tags(:general))
   end
 
+  def test_delete_associate_when_deleting_from_has_many_through
+    count = posts(:thinking).tags.count
+    tags_before = posts(:thinking).tags
+    tag = Tag.create!(:name => 'doomed')
+    post_thinking = posts(:thinking)
+    post_thinking.tags << tag
+    assert_equal(count + 1, post_thinking.tags(true).size)
+
+    assert_nothing_raised { post_thinking.tags.delete(tag) }    
+    assert_equal(count, post_thinking.tags.size)
+    assert_equal(count, post_thinking.tags(true).size)
+    assert_equal(tags_before.sort, post_thinking.tags.sort)
+  end
+
+  def test_delete_associate_when_deleting_from_has_many_through_with_multiple_tags
+    count = posts(:thinking).tags.count
+    tags_before = posts(:thinking).tags
+    doomed = Tag.create!(:name => 'doomed')
+    doomed2 = Tag.create!(:name => 'doomed2')
+    quaked = Tag.create!(:name => 'quaked')
+    post_thinking = posts(:thinking)
+    post_thinking.tags << doomed << doomed2
+    assert_equal(count + 2, post_thinking.tags(true).size)
+
+    assert_nothing_raised { post_thinking.tags.delete(doomed, doomed2, quaked) }    
+    assert_equal(count, post_thinking.tags.size)
+    assert_equal(count, post_thinking.tags(true).size)
+    assert_equal(tags_before.sort, post_thinking.tags.sort)
+  end
+
+  def test_deleting_junk_from_has_many_through_should_raise_type_mismatch
+    assert_raise(ActiveRecord::AssociationTypeMismatch) { posts(:thinking).tags.delete("Uhh what now?") }
+  end
 
   def test_has_many_through_sum_uses_calculations
     assert_nothing_raised { authors(:david).comments.sum(:post_id) }