title: iPhone NSPredicate how to create a predicate that checks if property has a value?
body: <p>This may be a silly question, but until now all of my NSPredicate had some sort of a key given to them:</p>
  
  <pre><code>@"SELF.typeRelationship.categoryType != %d";
  </code></pre>
  
  <p>Now I need to create a predicate that would pull all objects from the core data that have a value assigned to them. Any value would do. </p>
  
  <p>Will my predicate look like:</p>
  
  <pre><code>@"SELF.typeRelationship.categoryType != 0";
  @"SELF.typeRelationship.categoryType != nil";//if an object property?
  </code></pre>
  
  <p>, or <strong>is there some better format that I should use to check if a property has an object assigned to it?</strong></p>