title: Test type of NSNotification
body: <p>I need to check whether an object is an NSNotification. It is not enough to know if it is a subclass, as I want to differentiate between whether it is an NSNotification or a subclass of NSNotification.</p>
  
  <p>So to elaborate I need to differentiate between the following:</p>
  
  <ol>
  <li>An NSConcreteNotification</li>
  <li>A Subclass of NSNotification (But not NSConcreteNotification)</li>
  </ol>
  
  <p>The problem is that NSNotifications are actually NSConcreteNotifications and NSConcreteNotification is a private class so I can't use it to test against.</p>
  
  <pre><code>[object isMemberOfClass: [NSNotification class]] // returns NO in both cases
  [object isKindOfClass: [NSNotification class]] // returns YES in both cases
  </code></pre>