From f31ea4df3ac760ab7ff18ea439e9a9ce9b8c625a Mon Sep 17 00:00:00 2001
From: John Foley <john@thefol.io>
Date: Sun, 23 Sep 2012 12:49:34 -0600
Subject: Add CHANGELOG entry and update the guide

---
 guides/source/active_record_validations_callbacks.md | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'guides/source')

diff --git a/guides/source/active_record_validations_callbacks.md b/guides/source/active_record_validations_callbacks.md
index e5957d8acb..f32c1050ce 100644
--- a/guides/source/active_record_validations_callbacks.md
+++ b/guides/source/active_record_validations_callbacks.md
@@ -995,6 +995,25 @@ class User < ActiveRecord::Base
 end
 ```
 
+Callbacks can also be registered to only fire on certain lifecycle events:
+<ruby>
+class User < ActiveRecord::Base
+  before_validation :normalize_name, :on => :create
+  
+  # :on takes an array as well
+  after_validation :set_location, :on => [ :create, :update ]
+
+  protected
+  def normalize_name
+    self.name = self.name.downcase.titleize
+  end
+
+  def set_location
+    self.location = LocationService.query(self)
+  end
+end
+</ruby>
+
 It is considered good practice to declare callback methods as protected or private. If left public, they can be called from outside of the model and violate the principle of object encapsulation.
 
 Available Callbacks
-- 
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