title: Guard statement in swift for error handling
body: <p>I tried running below statement, but it's skipped right over in the code. </p>
  
  <pre><code>guard let num1 = num1Input.text else
  {
      show("No input in first box")
      return
  }
  </code></pre>
  
  <p>Can somebody tell me why this statement isn't running when the text field is blank?</p>