title: Conditionally following a segue
body: <p>In my app I have a login screen. When connecting a segue from the login button to the next (table) view controller however, you are always able to proceed, no matter what you type in as login information. How can I check the login information and then decide whether to perform the segue or not, so how to perform the segue conditionally?</p>
  
  <p>Is it possible to achieve this while working with a segue? I know it can be done programmatically, but then I need another navigation controller cause I need a navigation bar..</p>