title: Convert Array to String and back to Array
body: <p>I have built a presenter class whose only job is to convert a given array into a string. I am test driving the solution, so I started with <code>"[nil, nil, nil]"</code> but each <code>nil</code> will eventually be replaced with letter. That functionality is being handled by another class.</p>
  
  <p>I am trying now to build an interface whose only job is to convert that string back to an array. So I will need to convert e.g. <code>"[\"a\", \"b\", nil]"</code> back to <code>["a", "b", nil]</code>. But I am stuck.</p>
  
  <p>For example, I'd like to convert </p>
  
  <pre><code>"[nil, nil, nil]"
  </code></pre>
  
  <p>to</p>
  
  <pre><code> [nil, nil, nil]
  </code></pre>
  
  <p>How could I do it?</p>