title: What is the difference between setObject:forKey setObject:forKeyedSubscript
body: <p>Is there any difference between the methods <code>setObject:forKey</code> and <code>setObject:forKeyedSubscript</code>? </p>
  
  <p>I am using an Objective-C <code>NSMutableArray</code>. Both seem to function the same way to me.</p>