Added #hash method for ObjectID.

README.rdoc

@@ -356,6 +356,9 @@ Les Hill, leshill on github
 Sean Cribbs, seancribbs on github
 * Modify standard_benchmark to allow profiling
 
+Sunny Hirai
+* Suggested hashcode fix for Mongo::ObjectID
+
 = License
 
  Copyright 2008-2009 10gen Inc.

lib/mongo/types/objectid.rb

@@ -57,6 +57,12 @@ module Mongo
     end
     alias_method :==, :eql?
 
+    # Returns a unique hashcode for the object.
+    # This is required since we've defined an #eql? method.
+    def hash
+      @data.hash
+    end
+
     def to_a
       @data.dup
     end

test/test_objectid.rb

@@ -7,7 +7,18 @@ class ObjectIDTest < Test::Unit::TestCase
   include Mongo
 
   def setup
-    @o = ObjectID.new()
+    @o = ObjectID.new
+  end
+
+  def test_hashcode
+    assert_equal @o.instance_variable_get(:@data).hash, @o.hash
+  end
+
+  def test_array_uniq_for_equilavent_ids
+    a = ObjectID.new('123')
+    b = ObjectID.new('123')
+    assert_equal a, b
+    assert_equal 1, [a, b].uniq.size
   end
 
   def test_create_pk_method