title: Core Data lightweight migration: Can't find or automatically infer mapping model for migration
body: <p>So I created a new version of my data model, and made a previously optional field non-optional (giving it a default value). According to the documentation, this should mean my migration is eligible for lightweight, automatic migration.</p>
  
  <p>I also added options that allow this when I open the store, also per the documentation:</p>
  
  <pre><code>NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
  
  [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
  
  [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
  </code></pre>
  
  <p>When my app is starting, however, I get the following error: </p>
  
  <blockquote>
    <p>"Can't find or automatically infer mapping model for migration".</p>
  </blockquote>
  
  <p>Does anyone know what the problem here could be? Any help is appreciated... thanks!</p>