Parse findObjectsInBackgroundWithBlock return nil

Question

This is my code in swift

class UserViewController: UITableViewController {

var userArray: NSMutableArray = []

@IBOutlet weak var friendListTableView: UITableView!
override func viewDidLoad() {
    super.viewDidLoad()

       retrieveMessages()

   }
func retrieveMessages() {
    var query = PFUser.query()
    if let username = PFUser.currentUser().username {
        query.whereKey("username", equalTo: username)
        query.findObjectsInBackgroundWithBlock {
        (objects, error) -> Void in

        for object in objects! {
            let usernames:String? = (object as PFObject)["Friends"] as? String
            println(usernames)
            if usernames != nil {
                self.userArray.addObject(usernames!)
            }
        }
                dispatch_async(dispatch_get_main_queue()) {
                    self.friendListTableView.reloadData()
                }

    }

}
}
            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 Potentially incomplete method implementation.
    // Return the number of sections.
    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete method implementation.
    // Return the number of rows in the section.
    return userArray.count
}


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    // Update - replace as with as!

    let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as UITableViewCell

    cell.textLabel?.text = userArray[indexPath.row] as? String

    return cell
}

the problem is the findObjectsInBackgroundWithBlock method return nil so my table won't update,the object contains array of friends that current user had. So how do I fix this? thanks in advance and let me know if you need more information!

Update: I've change my code to (I'm using Xcode 6.2)

class UserTableViewController: UITableViewController {

var userArray: [String] = []
override func viewDidLoad() {
    super.viewDidLoad()
    retrieveMessages()
}

func retrieveMessages() {
    var query = PFUser.query()!
    if let username = PFUser.currentUser()!.username {
        query.whereKey("username", equalTo: username)
        query.findObjectsInBackgroundWithBlock { [weak self]
            (objects, error) -> Void in
            println(objects)
            for object in objects! {
                let username:String? = (object as PFUser).username
                if username != nil {
                    self!.userArray.append(username!)
                }
            }
            self!.tableView.reloadData()
        }

    }
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    return userArray.count
}


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("userCell", forIndexPath: indexPath) as UITableViewCell

    cell.textLabel?.text = userArray[indexPath.row]

    return cell
}

and my app crash, this is the error log

2015-06-08 01:41:32.944 ParseStarterProject[635:14183] Unknown class _TtC19ParseStarterProject18UserViewController in Interface Builder file. 2015-06-08 01:41:32.966 ParseStarterProject[635:14183] * Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key friendListTableView.' * First throw call stack: ( 0 CoreFoundation 0x000000010d35fa75 exceptionPreprocess + 165 1 libobjc.A.dylib 0x000000010efeabb7 objc_exception_throw + 45 2 CoreFoundation 0x000000010d35f6b9 -[NSException raise] + 9 3 Foundation 0x000000010d803d43 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 259 4 CoreFoundation 0x000000010d2a95e0 -[NSArray makeObjectsPerformSelector:] + 224 5 UIKit 0x000000010dfec4ed -[UINib instantiateWithOwner:options:] + 1506 6 UIKit 0x000000010de4aa88 -[UIViewController _loadViewFromNibNamed:bundle:] + 242 7 UIKit 0x000000010de4b078 -[UIViewController loadView] + 109 8 UIKit 0x000000010e008bd8 -[UITableViewController loadView] + 76 9 UIKit 0x000000010de4b2e9 -[UIViewController loadViewIfRequired] + 75 10 UIKit 0x000000010de4b77e -[UIViewController view] + 27 11 UIKit 0x000000010e3eef4e -[_UIFullscreenPresentationController _setPresentedViewController:] + 65 12 UIKit 0x000000010de26d69 -[UIPresentationController initWithPresentedViewController:presentingViewController:] + 105 13 UIKit 0x000000010de57531 -[UIViewController _presentViewController:withAnimationController:completion:] + 1746 14 UIKit 0x000000010de59871 __62-[UIViewController presentViewController:animated:completion:]_block_invoke + 132 15 UIKit 0x000000010de59795 -[UIViewController presentViewController:animated:completion:] + 229 16 ParseStarterProject 0x000000010c81c1c0 _TFC19ParseStarterProject14ViewController13viewDidAppearfS0_FSbT_ + 1488 17 ParseStarterProject 0x000000010c81c231 _TToFC19ParseStarterProject14ViewController13viewDidAppearfS0_FSbT_ + 49 18 UIKit 0x000000010de4f361 -[UIViewController _setViewAppearState:isAnimating:] + 567 19 UIKit 0x000000010de4feab -[UIViewController _executeAfterAppearanceBlock] + 52 20 UIKit 0x000000010dd48adb _applyBlockToCFArrayCopiedToStack + 314 21 UIKit 0x000000010dd48974 _afterCACommitHandler + 547 22 CoreFoundation 0x000000010d294507 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 23 23 CoreFoundation 0x000000010d294460 __CFRunLoopDoObservers + 368 24 CoreFoundation 0x000000010d28a293 __CFRunLoopRun + 1123 25 CoreFoundation 0x000000010d289bc6 CFRunLoopRunSpecific + 470 26 GraphicsServices 0x0000000110a99a58 GSEventRunModal + 161 27 UIKit 0x000000010dd25580 UIApplicationMain + 1282 28 ParseStarterProject 0x000000010c8203ae top_level_code + 78 29 ParseStarterProject 0x000000010c82048a main + 42 30 libdyld.dylib 0x000000010f802145 start + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

Update: fix the error and these are screenshots of my parse my parse's class "User" https://www.dropbox.com/s/6xp48v3yn0l2hje/Screen%20Shot%202015-06-03%20at%202.10.13%20PM.png?dl=0 This is my current user's friend list inside "Friends" column https://www.dropbox.com/s/pd8mt8sf35u1m0v/Screen%20Shot%202015-06-03%20at%202.10.55%20PM.png?dl=0

What investigation have you done? What were the results? What does println(usernames) print? Did you inspect the error object? What does that say? How do you know the result shouldn't be nil? Does this user have any friends? — Aaron Brager
Does the code crash? Because if the result is nil, objects! should throw an error — Rajeev Bhatia
@sin90 give some info about whether you are getting any error or app crashes or not... — Himanshu gupta
the println(usernames) returns nil and I know it shouldn't be nil because I've saved user's friend list in parse and when I check it at the parse web site, it exists inside Friends column of parse's class name "User" and no, my app did not crash, but the method itself didn't get any object so my tableview's empty — sin90
I want to retrieve my friends column in User's class, I've update my code and my app crash, error log's in the question. any help is appreciated thank you! — sin90

Audrey Li Audrey Li · Accepted Answer · 2015-06-07T16:50:41

PFUser.query only queries the User table. It looks like what you really want to query is "Friends" table or a "Messages" table. Different queries have different types of objects to cast to, e.g. PFObject, PFUser... If you do want to query User table, you can find the working code below:

import UIKit
import Parse

class UserTableViewController: UITableViewController {

    var userArray = ["Jane","Ann"]
    override func viewDidLoad() {
        super.viewDidLoad()
         retrieveMessages()
    }

    func retrieveMessages() {
        var query = PFUser.query()!
        if let username = PFUser.currentUser()!.username {
            query.whereKey("username", equalTo: username)
            query.findObjectsInBackgroundWithBlock { [weak self]
                (objects, error) -> Void in
                println(objects)
                for object in objects! {
                    let username:String? = (object as! PFUser).username
                    if username != nil {
                        self!.userArray.append(username!)
                    }
                }
                self!.tableView.reloadData()
            }

        }
    }
    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return userArray.count
    }


    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("userCell", forIndexPath: indexPath) as! UITableViewCell

        cell.textLabel?.text = userArray[indexPath.row]

        return cell
    }
}

If you want to query other table, you have to change PFUser.query to PFQuery. I recently went through the same problem. You can find the sample code I wrote here

Parse findObjectsInBackgroundWithBlock return nil

1 Answers