title: Call can throw, but it is not marked with 'try' and the error is not handled: NSRegularExpression
body: <p>I have written this function in String Extension and can't figure out the error.</p>
  
  <pre><code>func isEmail() -&gt; Bool {
      let regex = NSRegularExpression(pattern: "^[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,4}$", options: [.CaseInsensitive])
  
      return regex.firstMatchInString(self, options: nil, range: NSMakeRange(0, characters.count)) != nil
  }
  </code></pre>
  
  <p>The error is:</p>
  
  <blockquote>
    <p>Call can throw, but it is not marked with 'try' and the error is not handled</p>
  </blockquote>