title: How to represent an optional Bool (Bool?) in Objective-C?
body: <p>I am trying to write a protocol in swift</p>
  
  <pre><code>@objc protocol RestAPIManagerDelegate {
  
        optional func credentialValidated(isValid: Bool?)
  }
  </code></pre>
  
  <p>But I am getting following error:</p>
  
  <pre><code>'Method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C'
  </code></pre>
  
  <p>Any suggestion?</p>