Add only_deleted scope and associated methods.

This patch makes it easy to get only the deleted records from a model class. This facilitates the creation of deleted records listings for "undelete"-like functionalities in your apps.

Added methods: find_only_deleted, count_only_deleted and exists_only_deleted?

Passing tests included (tested with activerecord 2.1).

lib/caboose/acts/paranoid.rb

@@ -19,6 +19,9 @@ module Acts #:nodoc:
     #   Widget.find(:all, :with_deleted => true)
     #   # SELECT * FROM widgets
     #
+    #   Widget.find_only_deleted(:all)
+    #   # SELECT * FROM widgets WHERE widgets.deleted_at IS NOT NULL
+    #
     #   Widget.find_with_deleted(1).deleted?
     #   # Returns true if the record was previously destroyed, false if not 
     #
@@ -31,6 +34,9 @@ module Acts #:nodoc:
     #   Widget.count_with_deleted
     #   # SELECT COUNT(*) FROM widgets
     #
+    #   Widget.count_only_deleted
+    #   # SELECT COUNT(*) FROM widgets WHERE widgets.deleted_at IS NOT NULL
+    #
     #   Widget.delete_all
     #   # UPDATE widgets SET deleted_at = '2005-09-17 17:46:36'
     #
@@ -87,14 +93,35 @@ def find_with_deleted(*args)
             end
           end
 
+          def find_only_deleted(*args)
+            options = args.extract_options!
+            validate_find_options(options)
+            set_readonly_option!(options)
+            options[:only_deleted] = true # yuck!
+
+            case args.first
+              when :first then find_initial(options)
+              when :all   then find_every(options)
+              else             find_from_ids(args, options)
+            end
+          end
+
           def exists?(*args)
             with_deleted_scope { exists_with_deleted?(*args) }
           end
 
+          def exists_only_deleted?(*args)
+            with_only_deleted_scope { exists_with_deleted?(*args) }
+          end
+
           def count_with_deleted(*args)
             calculate_with_deleted(:count, *construct_count_options_from_args(*args))
           end
 
+          def count_only_deleted(*args)
+            with_only_deleted_scope { count_with_deleted(*args) }
+          end
+
           def count(*args)
             with_deleted_scope { count_with_deleted(*args) }
           end
@@ -116,12 +143,18 @@ def with_deleted_scope(&block)
               with_scope({:find => { :conditions => ["#{table_name}.#{deleted_attribute} IS NULL OR #{table_name}.#{deleted_attribute} > ?", current_time] } }, :merge, &block)
             end
 
+            def with_only_deleted_scope(&block)
+              with_scope({:find => { :conditions => ["#{table_name}.#{deleted_attribute} IS NOT NULL AND #{table_name}.#{deleted_attribute} <= ?", current_time] } }, :merge, &block)
+            end
+
           private
             # all find calls lead here
             def find_every(options)
               options.delete(:with_deleted) ? 
                 find_every_with_deleted(options) :
-                with_deleted_scope { find_every_with_deleted(options) }
+                options.delete(:only_deleted) ? 
+                  with_only_deleted_scope { find_every_with_deleted(options) } :
+                  with_deleted_scope { find_every_with_deleted(options) }
             end
         end
 

test/paranoid_test.rb

@@ -47,9 +47,15 @@ def test_should_exists_with_deleted
     assert !Widget.exists?(2)
   end
 
+  def test_should_exists_only_deleted
+    assert Widget.exists_only_deleted?(2)
+    assert !Widget.exists_only_deleted?(1)
+  end
+
   def test_should_count_with_deleted
     assert_equal 1, Widget.count
     assert_equal 2, Widget.count_with_deleted
+    assert_equal 1, Widget.count_only_deleted
     assert_equal 2, Widget.calculate_with_deleted(:count, :all)
   end
 
@@ -69,6 +75,7 @@ def test_should_destroy
     widgets(:widget_1).destroy!
     assert_equal 0, Widget.count
     assert_equal 0, Category.count
+    assert_equal 1, Widget.count_only_deleted
     assert_equal 1, Widget.calculate_with_deleted(:count, :all)
     # Category doesn't get destroyed because the dependent before_destroy callback uses #destroy
     assert_equal 4, Category.calculate_with_deleted(:count, :all)
@@ -113,6 +120,12 @@ def test_should_not_count_deleted
     assert_equal 1, Widget.count
     assert_equal 1, Widget.count(:all, :conditions => ['title=?', 'widget 1'])
     assert_equal 2, Widget.calculate_with_deleted(:count, :all)
+    assert_equal 1, Widget.count_only_deleted
+  end
+
+  def test_should_find_only_deleted
+    assert_equal [2], Widget.find_only_deleted(:all).collect { |w| w.id }
+    assert_equal [1, 2], Widget.find_with_deleted(:all, :order => 'id').collect { |w| w.id }
   end
 
   def test_should_not_find_deleted