Merge pull request #1860 from dmathieu/comparison

Allow comparison on model objects - Closes #1858

2 files changed, 22 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index ebea4252f9..fd52038647 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1811,6 +1811,15 @@ MSG
         @attributes.frozen?
       end
 
+      # Allows sort on objects
+      def <=>(other_object)
+        if other_object.is_a?(self.class)
+          self.to_key <=> other_object.to_key
+        else
+          nil
+        end
+      end
+
       # Backport dup from 1.9 so that initialize_dup() gets called
       unless Object.respond_to?(:initialize_dup)
         def dup # :nodoc:
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 2224097f04..5fef3faab9 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -478,6 +478,19 @@ class BasicsTest < ActiveRecord::TestCase
   def test_hashing
     assert_equal [ Topic.find(1) ], [ Topic.find(2).topic ] & [ Topic.find(1) ]
   end
+  
+  def test_comparison
+    topic_1 = Topic.create!
+    topic_2 = Topic.create!
+    
+    assert_equal [topic_2, topic_1].sort, [topic_1, topic_2]
+  end
+
+  def test_comparison_with_different_objects
+    topic = Topic.create
+    category = Category.create(:name => "comparison")
+    assert_nil topic <=> category
+  end
 
   def test_readonly_attributes
     assert_equal Set.new([ 'title' , 'comments_count' ]), ReadonlyTitlePost.readonly_attributes