From d71f7d4e3a441c5577dfed0faf98957ff780325f Mon Sep 17 00:00:00 2001
From: Kyle Banker <kylebanker@gmail.com>
Date: Fri, 22 Jan 2010 14:56:00 -0500
Subject: [PATCH] support MongoDB extended JSON on ObjectID#to_json

---
 lib/mongo/types/objectid.rb | 8 ++++++--
 test/test_objectid.rb       | 2 +-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/lib/mongo/types/objectid.rb b/lib/mongo/types/objectid.rb
index fad5f8d..a89fcc5 100644
--- a/lib/mongo/types/objectid.rb
+++ b/lib/mongo/types/objectid.rb
@@ -142,8 +142,12 @@ module Mongo
     end
     alias_method :inspect, :to_s
 
-    def to_json(*args)
-      %Q("#{to_s}")
+    # Convert to MongoDB extended JSON format. Since JSON includes type information,
+    # but lacks an ObjectID type, this JSON format encodes the type using an $id key.
+    #
+    # @return [String] the object id represented as MongoDB extended JSON.
+    def to_json(escaped=false)
+      "{\"$oid\": \"#{to_s}\"}"
     end
 
     # @deprecated
diff --git a/test/test_objectid.rb b/test/test_objectid.rb
index 5e49877..3156937 100644
--- a/test/test_objectid.rb
+++ b/test/test_objectid.rb
@@ -151,6 +151,6 @@ class ObjectIDTest < Test::Unit::TestCase
 
   def test_json
     id = ObjectID.new
-    assert_equal %Q("#{id}"), id.to_json
+    assert_equal "{\"$oid\": \"#{id}\"}", id.to_json
   end
 end