title: Parse.com - dictionary with quotation marks in key name -> error
body: <p>When attempting to save a PFObject, I was receiving the error <code>"Error: object not found for update (Code: 101, Version: 1.2.15)"</code> (logged automatically), and the localized description was logging: <code>The operation couldn’t be completed. (Parse error 101.)</code></p>
  
  <p>I eventually isolated the problem: the <code>NSDictionary</code> I was assigning to one of the fields on the PFObject had quotation marks around key names; turns out these are added automatically by the <code>NSDictionary</code> class when a key name contains nonalphanumeric characters.</p>
  
  <p>Here's an example of a (logged) PFObject whose save was giving an error:</p>
  
  <pre><code>"&lt;PlaybackPositionTracker:MKXTjOXg07:(null)&gt; {\n ACL = \"&lt;PFACL: 0xc1e80f0&gt;\";\n aclRead = (\n \"\"\n );\n aclWrite = (\n \"\"\n );\n deletedAt = \"&lt;null&gt;\";\n nowPlaying = \"&lt;null&gt;\";\n playbackPositionDictionary = {\n \"http://podcastdownload.npr.org/anon.npr-podcasts/podcast/35/290491304/npr_290491304.mp3\" = 0;\n };\n}"
  </code></pre>
  
  <p>I suppose Parse interprets quotation marks to indicate a link to another Parse object or something (or else I'm at a loss to explain why this gives the "<code>object not found</code>" error).</p>
  
  <p>How can I use a url string as a key in a dictionary that is assigned to a field on a PFObject? I could remove all nonalphanumeric characters from the string, but that would be a messy solution. What other options might there be? Thank you.</p>