title: iOS Are methods called by delegates and observers executed on the main thread?
body: <p>Sorry, I'm not sure of the right language here, but when methods are called because they are either delegate methods, or methods called as a result of being listed as the target of an observer, are they executed on the main thread?</p>
  
  <p>I'm wondering if I can just make UI changes in these methods, or do I have to wrap them in </p>
  
  <pre><code>    dispatch_async(dispatch_get_main_queue(), ^{ UI stuff });
  </code></pre>
  
  <p>TIA: John</p>