From 7e06494e32f944f8c99d7d21e17224509332ee6b Mon Sep 17 00:00:00 2001
From: Curtis Hawthorne <curtis@thefjord.org>
Date: Sun, 21 Feb 2010 22:47:30 -0500
Subject: Destroy respects optimistic locking.

Now works with :dependent => :destroy and includes unit tests for that
case.  Also includes better error messages when updating/deleting stale
objects.

[#1966 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>
---
 .../lib/active_record/locking/optimistic.rb        | 35 +++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

(limited to 'activerecord/lib/active_record/locking/optimistic.rb')

diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index 9044ca418b..60ad23f38c 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -23,6 +23,16 @@ module ActiveRecord
     #   p2.first_name = "should fail"
     #   p2.save # Raises a ActiveRecord::StaleObjectError
     #
+    # Optimistic locking will also check for stale data when objects are destroyed.  Example:
+    #
+    #   p1 = Person.find(1)
+    #   p2 = Person.find(1)
+    #
+    #   p1.first_name = "Michael"
+    #   p1.save
+    #
+    #   p2.destroy # Raises a ActiveRecord::StaleObjectError
+    #
     # You're then responsible for dealing with the conflict by rescuing the exception and either rolling back, merging,
     # or otherwise apply the business logic needed to resolve the conflict.
     #
@@ -39,6 +49,7 @@ module ActiveRecord
         self.lock_optimistically = true
 
         alias_method_chain :update, :lock
+        alias_method_chain :destroy, :lock
         alias_method_chain :attributes_from_column_definition, :lock
 
         class << self
@@ -88,7 +99,7 @@ module ActiveRecord
 
 
             unless affected_rows == 1
-              raise ActiveRecord::StaleObjectError, "Attempted to update a stale object"
+              raise ActiveRecord::StaleObjectError, "Attempted to update a stale object: #{self.class.name}"
             end
 
             affected_rows
@@ -100,6 +111,28 @@ module ActiveRecord
           end
         end
 
+        def destroy_with_lock #:nodoc:
+          return destroy_without_lock unless locking_enabled?
+
+          unless new_record?
+            lock_col = self.class.locking_column
+            previous_value = send(lock_col).to_i
+
+            affected_rows = connection.delete(
+              "DELETE FROM #{self.class.quoted_table_name} " +
+              "WHERE #{connection.quote_column_name(self.class.primary_key)} = #{quoted_id} " +
+                  "AND #{self.class.quoted_locking_column} = #{quote_value(previous_value)}",
+              "#{self.class.name} Destroy"
+            )
+
+            unless affected_rows == 1
+              raise ActiveRecord::StaleObjectError, "Attempted to delete a stale object: #{self.class.name}"
+            end
+          end
+
+          freeze
+        end
+
       module ClassMethods
         DEFAULT_LOCKING_COLUMN = 'lock_version'
 
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