title: iOS: Make segue wait for login success
body: <p>I am designing an iOS app using XCode 4.2's storyboard feature. The app has a login screen that takes a username and password and has a button to log in. Pushing the login button triggers a push seque to another view controller. However, I want the seque to wait until the login comes back successful before proceeding to the next view controller.</p>
  
  <p>I know about <code>prepareForSegue:sender:</code> but heres my issue: the login call is asynchronous. I therefore cannot perform the login there.</p>
  
  <p>Is there someway around this? Can I create a seque in the storyboard that is only triggered when I want it to be (as opposed to when a button is clicked)? </p>