title: Unable to use 'class' as a key in NSDictionary
body: <p>I'm trying to use a class as a key in an <code>NSDictionary</code>. I looked at the answer to <a href="https://stackoverflow.com/questions/730076/using-class-as-key-in-nsdictionary">this question</a> and what I have is pretty much the same; I'm using <code>setObject: forKey:</code>. However, XCode complains, saying <code>Incompatible pointer types sending 'Class' to parameter of type 'id&lt;NSCopying&gt;'</code>. The call I have is:</p>
  
  <pre><code>[_bugTypeToSerializerDictionary setObject: bugToStringSerializer 
                                  forKey: [bugToStringSerializer serializedObjectType]];
  </code></pre>
  
  <p><code>bugToStringSerializer</code> is an instance of <code>BugToStringSerializer</code> whose concrete implementations implement <code>serializedObjectType</code>. An example of a concrete implementation looks like this:</p>
  
  <pre><code>- (Class) serializedObjectType {
      return [InfectableBug class];
  }
  </code></pre>
  
  <p>What am I doing wrong here?</p>