How can I pass data to a viewcontroller and load it before pushing it onto Navigation stack?

问题

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.

回答1:

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.

来源：https://stackoverflow.com/questions/40953609/how-can-i-pass-data-to-a-viewcontroller-and-load-it-before-pushing-it-onto-navig