Query within query not appending with Swift/Parse - swift

Question

I hope someone can help because this is probably a simple problem, but my Parse query within a query prints the object I am looking for, but cannot append it to the array I need it in to retrieve it in a UITableView.
The error is "fatal error: index out of range" when I dequeue the results of the query in a cell.
Here's the code:
import UIKit
import Parse
import Bolts
class MessagesTableVC: UITableViewController {
var usernames = [String]()
var sentDate = [NSDate]()
var details = [String]()
var userImage = [PFFile]()
#IBAction func backToProfile(sender: AnyObject) {
self.performSegueWithIdentifier("messagesToProfile", sender: self)
}
override func viewDidLoad() {
super.viewDidLoad()
let messagesQuery = PFQuery(className: "Messages")
messagesQuery.whereKey("recipientId", equalTo: PFUser.currentUser()!.objectId!)
messagesQuery.includeKey("senderId")
messagesQuery.orderByDescending("createdAt")
messagesQuery.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if error != nil {
print(error)
}
if error == nil {
if let objects = objects {
self.usernames.removeAll(keepCapacity: true)
self.sentDate.removeAll(keepCapacity: true)
self.details.removeAll(keepCapacity: true)
self.userImage.removeAll(keepCapacity: true)
for object in objects {
self.sentDate.append(object.createdAt! as NSDate)
if (object["item"] != nil) {
self.details.append(object["item"] as! String)
} else {
self.details.append(object["request"] as! String)
}
let senderObject = (object["senderId"] as! PFUser)
let senderId = (senderObject.objectId! as String)
print(senderId)
// Query for sender info
let userQuery = PFUser.query()
userQuery?.whereKey("objectId", equalTo: senderId)
userQuery?.getFirstObjectInBackgroundWithBlock({ (object, error) in
self.usernames.append((object!["username"] as! String))
//self.userImage.append(object!["profilePicture"] as! PFFile)
})
}
dispatch_async(dispatch_get_main_queue()) {
self.tableView.reloadData()
//self.search.resignFirstResponder()
}
}
}
})
// Uncomment the following line to preserve selection between presentations
// self.clearsSelectionOnViewWillAppear = false
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
return sentDate.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("messageCell", forIndexPath: indexPath) as! MessageTableViewCell
//print(usernames[indexPath.row])
cell.senderUsername.text = usernames[indexPath.row]
cell.itemOrPreview.text = details[indexPath.row]
let date = sentDate[indexPath.row]
let formatter = NSDateFormatter()
formatter.dateStyle = NSDateFormatterStyle.LongStyle
formatter.timeStyle = .ShortStyle
let dateString = formatter.stringFromDate(date)
cell.sentDate.text = dateString
//userImage[indexPath.row].getDataInBackgroundWithBlock { (data, error) in
// if let downloadedItemImage = UIImage(data: data!) {
// cell.senderImage?.image = downloadedItemImage
//}
//}
return cell
}
override func viewWillAppear(animated: Bool) {
tableView.reloadData()
}
}

Answer 1

As I may guess, you might get inconsistent number of elements in sentDate and usernames because you append to usernames via asynchronous getFirstObjectInBackgroundWithBlock method, so, by the time you call reloadData on tableView, all user names might not be yet added to usernames. You might have less items in usernames then in sentDate by the time your tableView callback fires and in numberOfItems you return number of items in sentDate.
In order to fix that you need at first refactor your code, it has a lot of places things might go wrong. I won't give any specific advise, but, seems, you might want to wait before you get all the data before you reload your tableView.