title: Core Data - can't set empty string as default value for attribute
body: <p>I have an entity in my datamodel with a string attribute that is currently optional, and I'd like to convert this to a required attribute with a default value of the empty string.</p>
  <p>As others have discovered, leaving the default value blank in the Xcode Core Data data modeler results in validation errors (since the designer interprets this as NULL), but trying '', &quot;&quot;, or @&quot;&quot; as the default value results in those literal characters being interpreted as the default, rather than the empty zero-length string, as desired.</p>
  <p>I did find <a href="http://www.cocoabuilder.com/archive/cocoa/188754-using-an-empty-string-as-the-default-value-for-core-data-attribute-in-the-xcode-modeller.html" rel="nofollow noreferrer">this thread</a> on Google, however, apart from the solution being really ugly (model definition split between the <code>.xcdatamodel</code> and objc source), it also doesn't work for lightweight migrations because those migrations are done solely based on the <code>.xcdatamodel</code> files and the objc logic from your entity implementations isn't loaded.</p>
  <p>Is there any way to achieve this in the data model designer?</p>