How can I pass data to a viewcontroller and load i

I have a view controller with a collection view and when I click a cell, I pass a variable to another view controller, then push it onto the navigation stack.

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
     self.performSegueWithIdentifier("nextVC", sender: self.userArray[indexPath.row])
}

This is how I send the variable:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
     super.prepareForSegue(segue, sender: sender)
     let nextVC = segue.destinationViewController as! NextVC
     if let senderId = sender!.objectForKey("uId") {
          nextVC.userId = senderId as! String
     }
}

This next view controller (nextVC) has a lot of stuff on it. I have done everything I can to optimize it but it still takes some time to load all the stuff. Is there a way I can prepare for segue, pass the variable, and let the next vc do it's thing, then when it's done loading, actually segue to it? (or show it)? I saw some other questions which talk about preloading view controllers but none of them dealt with passing a variable. This variable is very important because all the stuff in the nextVC has to know this one variable (based on cell touched) or it won't be able to load. I hope I explained this well enough, thanks for your time.

If you access the view property of the destinationViewController, it will trigger the view to load. Since you don't really need the view, just assign it to _ to keep the compiler happy.

Try this:

 if let senderId = sender!.objectForKey("uId") {
      nextVC.userId = senderId as! String
      _ = nextVC.view
 }

This will trigger viewDidLoad to run before the segue happens. Make sure your code to set up your NextVC is in viewDidLoad and you should be good to go.