title: Perform some code before a segue after I push a button in swift
body: <p>I have a button that goes to another view. I want to perform some code before the segue moves. The problem I am facing is the segue goes to the other page before the code has a chance to finish. So the values that are in the User default don't get changed before the view gets changed. 
  My question is how can I get the code to run and after its done get the segue to fire?
  Here is what I have so far:</p>
  
  <pre><code> @IBAction func onLogoutClick(sender: AnyObject) {
      //clear all url chache 
      NSURLCache.sharedURLCache().removeAllCachedResponses()
      //null out everything for logout
      email = ""
      password = ""
      self.loginInformation.setObject(self.email, forKey: "email")
      self.loginInformation.setObject(self.password, forKey: "password")
      self.loginInformation.synchronize()
      //self.view = LoginView
  }
  </code></pre>