From c121e5b9cc82ed47f0bde503b5e01dc8681d9562 Mon Sep 17 00:00:00 2001
From: Ari Epstein <ate2@cornell.edu>
Date: Wed, 10 Nov 2010 15:08:22 -0500
Subject: [PATCH] Add accessors for _previously_changed?, previously_was, previous_change and a test to verify.

---
 activemodel/lib/active_model/dirty.rb |   21 +++++++++++++++++++--
 activemodel/test/cases/dirty_test.rb  |   15 +++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index 1dfd0b6..0a17062 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -90,7 +90,8 @@ module ActiveModel
     include ActiveModel::AttributeMethods
 
     included do
-      attribute_method_suffix '_changed?', '_change', '_will_change!', '_was'
+      attribute_method_suffix '_changed?', '_change', '_will_change!', '_was',
+        '_previously_changed?', '_previous_change', '_previously_was'
       attribute_method_affix :prefix => 'reset_', :suffix => '!'
     end
 
@@ -124,7 +125,7 @@ module ActiveModel
     #   person.save
     #   person.previous_changes # => {'name' => ['bob, 'robert']}
     def previous_changes
-      @previously_changed
+      @previously_changed ||= {}
     end
 
     # Map of change <tt>attr => original value</tt>.
@@ -149,6 +150,21 @@ module ActiveModel
         attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr)
       end
 
+      # Handle <tt>*_previously_changed?</tt> for +method_missing+.
+      def attribute_previously_changed?(attr)
+        previous_changes.keys.include?(attr)
+      end
+
+      # Handle <tt>*_previous_change</tt> for +method_missing+.
+      def attribute_previous_change(attr)
+        previous_changes[attr] if attribute_previously_changed?(attr)
+      end
+
+      # Handle <tt>*_previously_was</tt> for +method_missing+.
+      def attribute_previously_was(attr)
+        attribute_previously_changed?(attr) ? attribute_previous_change(attr).first : attribute_was(attr)
+      end
+
       # Handle <tt>*_will_change!</tt> for +method_missing+.
       def attribute_will_change!(attr)
         begin
@@ -166,3 +182,4 @@ module ActiveModel
       end
   end
 end
+
diff --git a/activemodel/test/cases/dirty_test.rb b/activemodel/test/cases/dirty_test.rb
index 858ae9c..851f9c1 100644
--- a/activemodel/test/cases/dirty_test.rb
+++ b/activemodel/test/cases/dirty_test.rb
@@ -106,4 +106,19 @@ class DirtyTest < ActiveModel::TestCase
     assert_equal [nil, "Jericho Cane"], @model.previous_changes['name']
   end
 
+  test "previous attribute accessors" do
+    @model.instance_variable_set("@name", "Yam")
+    assert !@model.name_changed?
+    assert !@model.name_previously_changed?
+    assert @model.name_previous_change.nil?
+    assert_equal "Yam", @model.name_previously_was
+    @model.name = "Bob"
+    @model.save
+    assert !@model.name_changed?
+    assert @model.name_previously_changed?
+    assert_equal ["Yam", "Bob"], @model.name_previous_change
+    assert_equal "Yam", @model.name_previously_was
+  end
+
 end
+
-- 
1.7.2.3