title: NSString remains in memory
body: <p>I have been converting the entered password into <code>NSString</code>.</p>
  
  <pre><code>NSString * tempStr = [[NSString alloc] initWithData: [[DummyEnc sharedInstance] decDummy] encoding: NSUTF8StringEncoding];
  ...
  ...
  
  tempStr = nil
  </code></pre>
  
  <p><code>NSString</code> is required because <code>tempStr</code> handles other logic.</p>
  
  <p>But there is a problem that <code>tempStr</code> remains in memory, how do I fix it?</p>
  
  <p>Is there a way I would like to use it as an <code>NSString</code>?</p>