Run code after a background process - parse.com - swift

Question

I have a findObjectsInBackgroundWithBlock method in my viewController. Now i want to execute code, but just until this background method is finished. How can i do that?
I'm using the swift programming lanuage.

Answer 1

Here is some example code that could help you. It is not clear how you would restrict the code (PRE-BACKGROUND CODE) to run only while the background processing has completed. You may want to insert some code in the notification response function either to confirm that that PRE-BACKGROUND CODE is completed or to terminate it.
// ParseTestViewController.swift
import UIKit
import Foundation
import Parse
class ParseTestViewController: UIViewController {
var userData = [String]()
func codeToExecuteBeforeStringsAreAppended() {
}
func codeToExecuteAfterStringsAreAppended() {
// can use the array 'userData'
}
override func viewDidLoad() {
NSNotificationCenter.defaultCenter().addObserver(self,
selector: "notificationResponse:",
name: "recordsLoaded",
object: nil
)
self.getUserdataForUsername("MyName")
/* ==========================
Insert code tto be executed immediately after making the call that must not use the data returned by Parse. The function returns right away and the background may not have completed.
*/
codeToExecuteBeforeStringsAreAppended()
}
func getUserdataForUsername (queryUserName: String) {
var query = PFQuery(className:"UserData")
query.whereKey("username", equalTo: queryUserName)
let notification = NSNotification(name: "userDataRetrieved", object: self)
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]?, error: NSError?) -> Void in
if error == nil {
for object in objects! {
if let username = object["username"] as? String {
self.userData.append (username)
}
}
} else {
// Log details of the failure
println("Error: \(error!) \(error!.userInfo!)")
}
NSNotificationCenter.defaultCenter().postNotification(notification)
}
}
func notificationResponse (notification: NSNotification) {
// this is executed after the background processing is done
// Insert the code that uses the data retrieved from Parse
codeToExecuteAfterStringsAreAppended()
NSNotificationCenter.defaultCenter().removeObserver(self)
}
}

Answer 2

This is pretty well covered in the documentation and guide on parse.com. But maybe you have a more specific question/scenario?
Guide to queries on parse.com
var query = PFQuery(className:"GameScore")
query.whereKey("playerName", equalTo:"Sean Plott")
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]?, error: NSError?) -> Void in
if error == nil {
// The find succeeded.
println("Successfully retrieved \(objects!.count) scores.")
// Do something with the found objects
if let objects = objects as? [PFObject] {
for object in objects {
println(object.objectId)
}
}
} else {
// Log details of the failure
println("Error: \(error!) \(error!.userInfo!)")
}
}
Edit: specific version for PFUser to array of usernames
var usernames: [String]?
func loadUsernames () {
if let query = PFUser.query() {
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]?, error: NSError?) -> Void in
if error == nil { // No error - should be good to go
self.userNames = (objects as! [PFUser]).map({$0.username!})
// Call/run any code you like here - remember 'self' keyword
// It will not run until userNames is populated
self.callSomeMethod()
} else { // Error - do something clever
}
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
loadUsernames()
}