From 8823ba5dfae7a117bd01d0e22c3de68f62f4d872 Mon Sep 17 00:00:00 2001
From: Scott Barr <scottb@globalitcreations.com>
Date: Fri, 15 May 2009 12:18:23 +0800
Subject: [PATCH] Added pending_changes to ActiveRecord::Dirty

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 # => {}
---
 activerecord/lib/active_record/dirty.rb |   17 ++++++++++++
 activerecord/test/cases/dirty_test.rb   |   42 ++++++++++++++++++++++++++++---
 2 files changed, 55 insertions(+), 4 deletions(-)

diff --git a/activerecord/lib/active_record/dirty.rb b/activerecord/lib/active_record/dirty.rb
index ac84f6b..ce142d6 100644
--- a/activerecord/lib/active_record/dirty.rb
+++ b/activerecord/lib/active_record/dirty.rb
@@ -67,6 +67,15 @@ module ActiveRecord
       changed_attributes.keys
     end
 
+    # Map of attributes that were changed when the model was saved.
+    #   person.name # => 'bob'
+    #   person.name = 'robert'
+    #   person.save
+    #   person.previous_changes # => {'name' => ['bob, 'robert']}
+    def previous_changes
+      previously_changed_attributes
+    end
+    
     # Map of changed attrs => [original value, new value].
     #   person.changes # => {}
     #   person.name = 'bob'
@@ -78,6 +87,7 @@ 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
@@ -86,6 +96,7 @@ module ActiveRecord
     # Attempts to <tt>save!</tt> the record and clears changed attributes if successful.
     def save_with_dirty!(*args) #:nodoc:
       status = save_without_dirty!(*args)
+      @previously_changed = changes
       changed_attributes.clear
       status
     end
@@ -93,6 +104,7 @@ module ActiveRecord
     # <tt>reload</tt> the record and clears changed attributes.
     def reload_with_dirty(*args) #:nodoc:
       record = reload_without_dirty(*args)
+      previously_changed_attributes.clear
       changed_attributes.clear
       record
     end
@@ -102,6 +114,11 @@ module ActiveRecord
       def changed_attributes
         @changed_attributes ||= {}
       end
+      
+      # Map of fields that were changed when the model was saved
+      def previously_changed_attributes
+        @previously_changed ||= {}
+      end
 
       # Handle <tt>*_changed?</tt> for +method_missing+.
       def attribute_changed?(attr)
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index ac95bac..3a7383e 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -31,24 +31,24 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.new
     assert !pirate.catchphrase_changed?
     assert_nil pirate.catchphrase_change
-
+    
     # Change catchphrase.
     pirate.catchphrase = 'arrr'
     assert pirate.catchphrase_changed?
     assert_nil pirate.catchphrase_was
     assert_equal [nil, 'arrr'], pirate.catchphrase_change
-
+    
     # Saved - no changes.
     pirate.save!
     assert !pirate.catchphrase_changed?
     assert_nil pirate.catchphrase_change
-
+    
     # Same value - no changes.
     pirate.catchphrase = 'arrr'
     assert !pirate.catchphrase_changed?
     assert_nil pirate.catchphrase_change
   end
-
+  
   def test_aliased_attribute_changes
     # the actual attribute here is name, title is an
     # alias setup via alias_attribute
@@ -288,6 +288,40 @@ class DirtyTest < ActiveRecord::TestCase
     end
   end
 
+  def test_previous_changes
+    # original values should be in previous_changes
+    pirate = Pirate.new
+    
+    assert_equal Hash.new, pirate.previous_changes
+    pirate.catchphrase = "arrr"
+    pirate.save!
+    
+    assert_equal 4, pirate.previous_changes.size
+    assert_equal [nil, "arrr"], pirate.previous_changes['catchphrase']
+    assert_equal [nil, pirate.id], pirate.previous_changes['id']
+    assert_nil pirate.previous_changes['updated_on'][0]
+    assert_not_nil pirate.previous_changes['updated_on'][1]
+    assert_nil pirate.previous_changes['created_on'][0]
+    assert_not_nil pirate.previous_changes['created_on'][1]
+    
+    # original values should be in previous_changes
+    pirate = Pirate.new
+    
+    assert_equal Hash.new, pirate.previous_changes
+    pirate.catchphrase = "arrr"
+    pirate.save
+    
+    assert_equal 4, pirate.previous_changes.size
+    assert_equal [nil, "arrr"], pirate.previous_changes['catchphrase']
+    assert_equal [nil, pirate.id], pirate.previous_changes['id']
+    assert pirate.previous_changes.include?('updated_on')
+    assert pirate.previous_changes.include?('created_on')
+    
+    pirate.catchphrase = "Yar!!"
+    pirate.reload
+    assert_equal Hash.new, pirate.previous_changes
+  end
+  
   private
     def with_partial_updates(klass, on = true)
       old = klass.partial_updates?
-- 
1.6.2.1