title: ruby on rails after_update callback hooks issue
body: <p>In my Rails Application, I have after_update callback. But this callback is executed when my record is first time created using save method and when it is updated using update_attributes.</p>
  
  <p>So I want a way using which the callback/method must be called when it is coming to update method but currently it is getting executing when it is coming to create as well as update method.</p>
  
  <p>I think update_attribute also call internally a save method, because of this issue is coming.</p>
  
  <p>So is there any way using which I can call my hook when record is updated and not saved.</p>
  
  <p>I found one way using attr_accessors but I wanted some other way as maintaining  these flags will be very difficult for my app</p>