title: CoreData get distinct values of Attribute
body: <p>I'm trying to setup my <code>NSFetchRequest</code> to core data to retrieve the unique values for a specific attribute in an entity.  i.e.</p>
  
  <p>an entity with the following information: </p>
  
  <pre><code>  name | rate | factor |
  _______|______|________|
  John   |  3.2 |    4   |
  Betty  |  5.5 |    7   |
  Betty  |  2.1 |    2   |
  Betty  |  3.1 |    2   |
  Edward |  4.5 |    5   |
  John   |  2.3 |    4   |
  </code></pre>
  
  <p>How would i set up the request to return an array with just: John, Betty, Edward?</p>