title: Text change notification for an NSTextField
body: <p>I would like to use the code from the answer to this question:  <a href="https://stackoverflow.com/questions/6527321/how-to-observe-the-value-of-an-nstextfield">How to observe the value of an NSTextField</a> on an NSTextField in order to observe changes on the string stored in the NSTextField.</p>
  
  <pre><code>[[NSNotificationCenter defaultCenter]
      addObserverForName:NSTextViewDidChangeSelectionNotification
      object:self.textView 
      queue:[NSOperationQueue mainQueue] 
      usingBlock:^(NSNotification *note){
      NSLog(@"Text: %@", self.textView.textStorage.string);
  }];
  </code></pre>
  
  <p>The class used here is an NSTextView. I can't find a notification in NSTextField to use instead of NSTextViewDidChangeSelectionNotification.</p>
  
  <p>Is there a notification available in NSTextField that can be used in this case ?</p>