title: writeToFile fails - how do I debug WHY it fails (what tools)?
body: <p>I'm getting an NSDictionary from JSON (using SBJson), and I want to store it. I'm using </p>
  
  <pre><code>[liveData writeToFile:localFilePath atomically:YES]
  </code></pre>
  
  <p>and it fails. The data <em>looks</em> like its all NSString, NSDictionary, and NSArray (which "atomically:YES" demands). I used the same  localFilePath elesewhere.</p>
  
  <p>So my question is: how can I find out where the problem is? What tools can I use to understand why writeToFile fails? The log doesn't show an error message. </p>