title: CoreData migration conception between two apps
body: <p>I've got big conception problem when it comes for updating my application. Here is what I've got now:</p>
  
  <ol>
  <li>An App with CoreData generated models, with given bundle id etc.</li>
  <li>Second App with CoreData generated models, with the SAME bundle id as in 1.</li>
  </ol>
  
  <p>Models between version 1 and 2 of the application differs in the manner that some relationships are deleted and some models aren't used (and deleted as well). I've just moved user settings to User defaults instead of fetching them from DB which was a costly operation.</p>
  
  <p>Now I've want to realease an update of my app (1) with my second version (2). I don't know how to make a migration in this scenario thou. I want to preserve the user settings and move them from model (1) to user defaults and repleace model (1) with model (2). </p>
  
  <p>I've read about migration in core data, but the examples all reflect on working with single project and creating the another version of core data models, which I'm unable to do as the (2) is completly new project (ofcourse I have access to source code of(1)).</p>
  
  <p>I was thinking about (correct me if there is better solution) of using two databases, fetching user settings from (1) and writting them to user defaults, then deleting database (1) and use only (2). If this is the correct way in my case, how I can use two different xcdatamodeld files in single project? </p>