title: SWIFT 5.1 Mutablecopy
body: <p>I wrote this code like this when I logged in, it is ok. but when I run again it is not working at all.
  in Xcode Version 11.2.1</p>
  
  <p><strong>this is my code:</strong></p>
  
  <pre class="lang-swift prettyprint-override"><code>var currentUser: NSMutableDictionary?     
  // saving logged info here
  currentUser = parsedJSON.mutableCopy() as? NSMutableDictionary
  UserDefaults.standard.set(currentUser, forKey: "currentUser")
  UserDefaults.standard.synchronize()
  </code></pre>