title: Qt: How do I set a QLineEdit's validator in the designer?
body: <p>I'm designing a UI at the moment, and I have a situation where I have a QLineEdit which I need to only accept integers.</p>
  
  <p>I know how to set the validator to use QIntValidator in code. But I'd like to do this in the designer.</p>
  
  <p>How can I set the QLineEdit's validator when using the designer?</p>
  
  <p>Note: I don't want to use an input mask. An input mask and a validator function differently.</p>