title: sectionNameKeyPath through multiple relationships
body: <p>I am working on an app that uses Core Data and an <code>NSFetchedResultsController</code>.  The model setup is like this:</p>
  
  <pre><code>/-----------\          /-----------\          /-----------\
  |Part       |          |Kit        |          |Source     |
  |-----------|          |-----------|          |-----------|
  |name       |          |name       |          |name       |
  |dimensions |          |description|          |location   |
  |...        |          |...        |          |...        |
  |-----------|          |-----------|          |-----------|
  |kits       | &lt;&lt;-\     |source     | &lt;&lt;-----1 |kits       |
  |           |     \-&gt;&gt; |parts      |          |           |
  \-----------/          \-----------/          \-----------/
  </code></pre>
  
  <p>So, a <code>Part</code> has a many-to-any relationship with a <code>Kit</code> (a part can be in one or more kits, and a kit can contain one or more parts).  And each <code>Kit</code> comes from a <code>Source</code> which may provide one or more <code>Kit</code>s.</p>
  
  <p>I am currently creating a <code>UITableView</code> that uses an <code>NSFetchedResultsController</code> with a simple listing of all of the <code>Part</code> objects.  I would like to group the parts into sections, with each section being a <code>Source</code>'s name.  I.e.:</p>
  
  <pre><code>|-------------------------------|
  |Source One                     |
  |-------------------------------|
  |Part One                       |
  |Part Two                       |
  |Part Three                     |
  |-------------------------------|
  |Source Two                     |
  |-------------------------------|
  |Part Four                      |
  |Part Two                       |
  |Part Five                      |
  |....                           |
  |-------------------------------|
  |             O                 |
  |-------------------------------|
  </code></pre>
  
  <p>Since a <code>Part</code> may come from multiple <code>Source</code>s, is it possible to do this with an NSFetchedResultsController by using the sectionNameKeyPath, or do I have to do this a completely different way?</p>
  
  <p>Thanks!</p>