title: What is an NSCFDictionary?
body: <p>I'm getting an NSCFDictionary returned to me and I can't figure out how to use it.  I know it's of type NSCFDictionary because I printed the class and it came out as __NCSFDictionary.  I can't figure out how to do anything with it.</p>
  
  <p>I'm just trying to hold onto it for now but can't even get that to work:</p>
  
  <pre><code>  NSDictionary *dict = [[NSURLCredentialStorage sharedCredentialStorage] allCredentials];
    for(NSURLProtectionSpace key in [dict keyEnumerator])
    {
           NSCFDictionary *value = [dict objectForKey:key];
    }
  </code></pre>
  
  <p>The class reference for allCredentials says its supposed to return a dictionary whose values are also dictionaries.  My assignment statement isn't working though.  Do I need a cast of some kind?</p>