How do you deal with Parse call off main thread when it needs to update UI and is being called at viewDidLoad?

Question

I'm really struggling with the multi-threading concept. All calls to Parse are done off the main thread which I understand is because you don't want to block the main thread while waiting for a reply. But what do I do if I need to get data from parse to update my UI before the screen is displayed?

I have subclassed PFUser to add additional fields so I want to get those additional fields and populate a the screen with the data so the user can modify their info

func getCurrentUser () -> ParseUser? {

    let currentUser = PFUser.currentUser()
    var user: ParseUser?

    let query = PFQuery(className:"_User")
    query.whereKey("objectId", equalTo: (currentUser.objectId!))
    query.findObjectsInBackgroundWithBlock  {
    (objects: [PFObject]?, error: NSError?) -> Void in

        dispatch_async(dispatch_get_main_queue()){
            if error == nil { 
            for object in objects! {
            user = object as! ParseUser
            }
        } else {
            print("Error: \(error!) \(error!.userInfo)")
            }
        }
    }
return user
print("user returned")

}

Answer 1

call this method before you display your view and write any changes to the display inside your dispatch_get_main_queue() block so your changes are reflected on the UI immediately. You've set your user object, no write to a UILabel or something with your User's name or whatever.