title: Is it safe to archive Dictionary with String as a key?
body: <p>According to Apple docs, hash value of string may not be stable across different invocations of app:</p>
  
  <blockquote>
    <p>The hash value is not guaranteed to be stable across different invocations of the same program. Do not persist the hash value across program runs.
    <a href="https://developer.apple.com/library/ios/documentation/Swift/Reference/Swift_String_Structure/index.html#//apple_ref/swift/structp/String/s:vSS9hashValueSi" rel="nofollow">Apple docs</a></p>
  </blockquote>
  
  <p>Is it safe to archive (by NSArchive) dictionary of the following type <code>[String: AnyObject]</code>?
  If so, how Dictionary prevents from instability? Does it archive dictionary as array of tuples, like <code>[(key, value)]</code>?</p>