From eb22c51173f3ebe0f5a53f8bc57ebc74e4f0a824 Mon Sep 17 00:00:00 2001
From: Damien Mathieu <42@dmathieu.com>
Date: Sun, 26 Jun 2011 09:41:30 +0200
Subject: comparing different classes returns nil

---
 activerecord/lib/active_record/base.rb | 6 +++++-
 activerecord/test/cases/base_test.rb   | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

(limited to 'activerecord')

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index a2b5a3ec4f..e970445082 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1806,7 +1806,11 @@ MSG
 
       # Allows sort on objects
       def <=>(other_object)
-        self.to_key <=> other_object.to_key
+        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
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 873c6d9678..5fef3faab9 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -486,6 +486,12 @@ class BasicsTest < ActiveRecord::TestCase
     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
 
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