title: Are NSNotificationCenter events received synchronously or asynchronously?
body: <p>If a class registers for <code>NSNotificationCenter</code> events of a certain type and another class posts an event of that type, will the code in the receiver execute before (synchronously) or after (asynchronously) the posting class continues? </p>
  
  <pre><code>- (void)poster {
      [[NSNotificationCenter defaultCenter]
          postNotificationWithName:@"myevent"
          object:nil];
      NSLog(@"Hello from poster");
  }
  
  - (void)receiver {
      [[NSNotificationCenter defaultCenter]
          addObserver:self
          selector:@selector:(mySelector)
          name:@"myevent"
          object:nil];
  }
  
  - (void) mySelector:(NSNotification *) notification {
      NSLog(@"Hello from receiver");
  }
  </code></pre>
  
  <p>In the code example above, will "Hello from receiver" be printed before or after "Hello from caller"?</p>