title: Changing value in nested dictionary in swift
body: <p>I am wondering why when setting the value of a nested dictionary, the containing dictionary does not reflect those changes? On line3, is a copy of the dictionary being returned?</p>
  
  <pre><code>var dic = Dictionary&lt;String, AnyObject&gt;()  // line1
  dic["key"] = ["a":"a"] // line2
  var dic2 = dic["key"] as Dictionary&lt;String, String&gt; // line3
  dic2["a"] = "b" // line4
  dic // key : ["a":"a"], would expect ["a":"b"]
  </code></pre>