title: How to use QMessageBox in Qt 5?
body: <p>So I am making a program in Qt 5.2.1 . What I need is, when the user clicks a button, a warning appears, if the user clicks 'Ok' then program continues and if he clicks 'Cancel' nothing happens.</p>
  
  <p>How do I do this? I'm a total newbie to Qt.</p>