title: guard let error: Initializer for conditional binding must have Optional type not 'String'
body: <p>I got fatal error While using guard let. Here's the error:</p>
  
  <blockquote>
    <p>Initializer for conditional binding must have Optional type not
    'String'</p>
  </blockquote>
  
  <p>Below my code which i have used:</p>
  
  <pre><code>@IBAction func signUpButtonPressed(sender: UIButton) {
      guard let email = emailTextField.text! where emailTextField.text!.characters.count &gt; 0 else {
          // alert
          return
      }
  
      guard let password = passwordTextField.text! where passwordTextField.text!.characters.count &gt; 0 else {
      // alert
         return
     }
  
       self.registerUserAsync(email, password: password)
  }
  </code></pre>