 <pre><code>class MyModel &lt; ActiveRecord::Base after_update :do_something attr_accessor :should_do_something def should_do_something? should_do_something != false end def do_something if should_do_something? ... end end end y = MyModel.new y.save! # callback is triggered n = MyModel.new n.should_do_something = false n.save! # callback isn't triggered </code></pre>