title: How to use uppercaseString, lowercaseString in Swift
body: <p>I have <code>Strings</code> and I want to convert to <code>uppercaseString</code>, <code>lowercaseString</code> with <code>only letters</code>.</p>
  
  <p>My strings;</p>
  
  <pre><code>let uppers  = " Hello*im ; + Upper+String "
  let lowers  = " Hello*im ; + Lower+String "
  print(uppers)
  print(lowers)
  </code></pre>
  
  <p><strong>Output of upper case looks like this</strong></p>
  
  <pre><code>HELLOIMUPPERSTRING 
  </code></pre>
  
  <p>Thank you !</p>