title: Core Data Migration error when migrating between non-consecutive versions
body: <h2>The Problem</h2>
  
  <ul>
  <li>I've got 13 versions of my core data model.</li>
  <li>I've made 13 mapping models (V1-V2, V2-V3 etc)</li>
  <li>I've got automatic migration switched on.</li>
  <li>On migration between two consecutive versions (e.g. V12-V13) the migration works perfectly</li>
  <li><p>On migration between two non-consecutive versions (e.g. V11-V13) the migration fails with the error:</p>
  
  <p><code>Can't find mapping model for migration</code></p></li>
  </ul>
  
  <h2>What I've tried</h2>
  
  <p>Creating a mapping model for every possible combination of versions. This works, but it's a real hassle.</p>
  
  <p>For version 14 I'll need to make 14 different mapping models. Manually. Ugh.</p>
  
  <h2>Code</h2>
  
  <p>Here's the options I pass in for migration:</p>
  
  <pre><code>[persistentStoreCoordinator addPersistentStoreWithType:[self storeType]
                                            configuration:nil 
                                                      URL:url 
                                                  options:[NSDictionary dictionaryWithObjectsAndKeys:
                                                           [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                                                           [NSNumber numberWithBool:NO], NSReadOnlyPersistentStoreOption,
                                                           nil]
                                                    error:&amp;error]){
  </code></pre>
  
  <h2>Data Model</h2>
  
  <p>My data model is pretty complex, but here it is: <a href="http://dl.dropbox.com/u/136780/Engine_V2_DataModel.xcdatamodeld.zip">http://dl.dropbox.com/u/136780/Engine_V2_DataModel.xcdatamodeld.zip</a></p>
  
  <p>I'm not using any version hash modifiers or renaming identifiers in my data model right now.</p>