title: Prevent dismissal of UIAlertController
body: <p>I am adding a <code>UITextField</code> to a <code>UIAlertController</code>, which appears as an <code>AlertView</code>. Before dismissing the <code>UIAlertController</code>, I want to validate the input of the <code>UITextField</code>. Based on the validation I want to dismiss the <code>UIAlertController</code> or not. But I have no clue how to prevent the dismissing action of the <code>UIAlertController</code> when a button is pressed. Has anyone solved this problem or any ideas where to start ? I went to google but no luck :/ Thanks! </p>