title: Observers vs. Callbacks
body: <p>i thought about using observers or callbacks.
  What and when you should use an observer?</p>
  
  <p>F.e. you could do following:</p>
  
  <pre><code># User-model
  class User &lt;&lt; AR
    after_create :send_greeting!
  
    def send_greeting!
      UserNotifier.deliver_greeting_message(self)
    end
  
  end
  
  #observer
  class UserNotifier &lt;&lt; AR
    def greeting_message(user)
    ...
    end
  end
  </code></pre>
  
  <p>or you could create an observer and let it watch when users becomes created...</p>
  
  <p>What dou you recommened?</p>