I added this feature so that a Map of changed fields could be retrieved

after a model had been saved. This is useful in the after_save callback
when you need to know what fields changed. At present there is no way
to do this other than have code in the before_save callback that takes
a copy of the changes Map, which I thought was a bit messy.

Example.

  person = Person.find_by_name('bob')
  person.name = 'robert'
  person.changes # => {'name' => ['bob, 'robert']}
  person.save
  person.changes # => {}
  person.previous_changes # => {'name' => ['bob, 'robert']}
  person.reload
  person.previous_changes # => {}

Signed-off-by: Joshua Peek <josh@joshpeek.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index b6c4df2a49..4df0f1af69 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -19,6 +19,7 @@ module ActiveRecord
       # Attempts to +save+ the record and clears changed attributes if successful.
       def save_with_dirty(*args) #:nodoc:
         if status = save_without_dirty(*args)
+          @previously_changed = changes
           changed_attributes.clear
         end
         status
@@ -26,12 +27,18 @@ module ActiveRecord
 
       # Attempts to <tt>save!</tt> the record and clears changed attributes if successful.
       def save_with_dirty!(*args) #:nodoc:
-        save_without_dirty!(*args).tap { changed_attributes.clear }
+        save_without_dirty!(*args).tap do
+          @previously_changed = changes 
+          changed_attributes.clear 
+        end
       end
 
       # <tt>reload</tt> the record and clears changed attributes.
       def reload_with_dirty(*args) #:nodoc:
-        reload_without_dirty(*args).tap { changed_attributes.clear }
+        reload_without_dirty(*args).tap do
+          previously_changed_attributes.clear
+          changed_attributes.clear
+        end
       end
 
       private