Use saved_changes if it’s present.

This change occured in ActiveRecord/Rails 5.1. Hunting for the deprecation raised in pat#1059 helped me debug this one (though that issue’s not yet resolved).

lib/thinking_sphinx/active_record/callbacks/update_callbacks.rb

@@ -1,6 +1,12 @@
 class ThinkingSphinx::ActiveRecord::Callbacks::UpdateCallbacks <
   ThinkingSphinx::Callbacks
 
+  if ActiveRecord::Base.instance_methods.grep(/saved_changes/).any?
+    CHANGED_ATTRIBUTES = lambda { |instance| instance.saved_changes.keys }
+  else
+    CHANGED_ATTRIBUTES = lambda { |instance| instance.changed }
+  end
+
   callbacks :after_update
 
   def after_update
@@ -15,14 +21,18 @@ def after_update
 
   def attributes_hash_for(index)
     updateable_attributes_for(index).inject({}) do |hash, attribute|
-      if instance.changed.include?(attribute.columns.first.__name.to_s)
+      if changed_attributes.include?(attribute.columns.first.__name.to_s)
         hash[attribute.name] = attribute.value_for(instance)
       end
 
       hash
     end
   end
 
+  def changed_attributes
+    @changed_attributes ||= CHANGED_ATTRIBUTES.call instance
+  end
+
   def configuration
     ThinkingSphinx::Configuration.instance
   end

spec/thinking_sphinx/active_record/callbacks/update_callbacks_spec.rb

@@ -40,7 +40,11 @@ module Callbacks; end
         double(:name => 'baz', :updateable? => false)
       ])
 
-      allow(instance).to receive_messages :changed => ['bar_column', 'baz'], :bar_column => 7
+      allow(instance).to receive_messages(
+        :changed       => ['bar_column', 'baz'],
+        :bar_column    => 7,
+        :saved_changes => {'bar_column' => [1, 2], 'baz' => [3, 4]}
+      )
     end
 
     it "does not send any updates to Sphinx if updates are disabled" do