title: mutable copy copies by reference, not value?
body: <p>Apparently mutableCopy copies by reference, not value. Ie if I do this:</p>
  
  <pre><code>NSMutableArray arrayA = [arrayB mutableCopy];
  </code></pre>
  
  <p>then change values of arrayB, then arrayA's values will also be changed.</p>
  
  <p>I think Java has a clone() method to copy by value.. is there an equivalent in objective c?</p>