Check that ActiveRecord exists before overriding methods.

lib/delayed/psych_ext.rb

@@ -1,8 +1,10 @@
-class ActiveRecord::Base
-  # serialize to YAML
-  def encode_with(coder)
-    coder["attributes"] = @attributes
-    coder.tag = ['!ruby/ActiveRecord', self.class.name].join(':')
+if defined?(ActiveRecord)
+  class ActiveRecord::Base
+    # serialize to YAML
+    def encode_with(coder)
+      coder["attributes"] = @attributes
+      coder.tag = ['!ruby/ActiveRecord', self.class.name].join(':')
+    end
   end
 end
 

lib/delayed/serialization/active_record.rb

@@ -1,17 +1,19 @@
-class ActiveRecord::Base
-  yaml_as "tag:ruby.yaml.org,2002:ActiveRecord"
+if defined?(ActiveRecord)
+  class ActiveRecord::Base
+    yaml_as "tag:ruby.yaml.org,2002:ActiveRecord"
 
-  def self.yaml_new(klass, tag, val)
-    if ActiveRecord::VERSION::MAJOR == 3
-      klass.unscoped.find(val['attributes'][klass.primary_key])
-    else # Rails 2
-      klass.with_exclusive_scope { klass.find(val['attributes'][klass.primary_key]) }
+    def self.yaml_new(klass, tag, val)
+      if ActiveRecord::VERSION::MAJOR == 3
+        klass.unscoped.find(val['attributes'][klass.primary_key])
+      else # Rails 2
+        klass.with_exclusive_scope { klass.find(val['attributes'][klass.primary_key]) }
+      end
+    rescue ActiveRecord::RecordNotFound
+      raise Delayed::DeserializationError
     end
-  rescue ActiveRecord::RecordNotFound
-    raise Delayed::DeserializationError
-  end
 
-  def to_yaml_properties
-    ['@attributes']
+    def to_yaml_properties
+      ['@attributes']
+    end
   end
-end
+end