From b9d56a5168dd83ee464109d24c4ff002e08415eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@gmail.com>
Date: Wed, 21 Dec 2011 09:11:04 +0100
Subject: [PATCH] Fix constant lookup when serializer is not available.

---
 lib/active_model_serializers.rb | 21 +++++++++++++--------
 test/serializer_support_test.rb | 11 +++++++++++
 2 files changed, 24 insertions(+), 8 deletions(-)
 create mode 100644 test/serializer_support_test.rb

diff --git a/lib/active_model_serializers.rb b/lib/active_model_serializers.rb
index 3019cd99f..b6248b375 100644
--- a/lib/active_model_serializers.rb
+++ b/lib/active_model_serializers.rb
@@ -5,14 +5,19 @@ module ActiveModel::SerializerSupport
   extend ActiveSupport::Concern
 
   module ClassMethods #:nodoc:
-    def active_model_serializer
-      return @active_model_serializer if defined?(@active_model_serializer)
-
-      # Use safe constantize when Rails 3.2 is out
-      begin
-        @active_model_serializer = "#{self.name}Serializer".constantize
-      rescue NameError => e
-        raise unless e.message =~ /uninitialized constant$/ && e.name.to_s == "#{self.name}Serializer"
+    if "".respond_to?(:safe_constantize)
+      def active_model_serializer
+        @active_model_serializer ||= "#{self.name}Serializer".safe_constantize
+      end
+    else
+      def active_model_serializer
+        return @active_model_serializer if defined?(@active_model_serializer)
+
+        begin
+          @active_model_serializer = "#{self.name}Serializer".constantize
+        rescue NameError => e
+          raise unless e.message =~ /uninitialized constant/
+        end
       end
     end
   end
diff --git a/test/serializer_support_test.rb b/test/serializer_support_test.rb
new file mode 100644
index 000000000..b2d2b8be4
--- /dev/null
+++ b/test/serializer_support_test.rb
@@ -0,0 +1,11 @@
+require "test_helper"
+
+class RandomModel
+  include ActiveModel::SerializerSupport
+end
+
+class SerializerSupportTest < ActiveModel::TestCase
+  test "it returns nil if no serializer exists" do
+    assert_equal nil, RandomModel.new.active_model_serializer
+  end
+end
\ No newline at end of file