解析findObjectsInBackgroundWithBlock返回nil

Question

这是我的代码迅速

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
}

问题是findObjectsInBackgroundWithBlock方法返回nil，所以我的表不会更新，该对象包含当前用户拥有的朋友数组。 那么我该如何解决呢？ 在此先感谢您，如果需要更多信息，请告诉我！

更新：我将代码更改为（我正在使用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
}

和我的应用程序崩溃，这是错误日志

2015-06-08 01：41：32.944 ParseStarterProject [635：14183] Interface Builder文件中的未知类_TtC19ParseStarterProject18UserViewController。 2015-06-08 01：41：32.966 ParseStarterProject [635：14183] *由于未捕获的异常'NSUnknownKeyException'而终止应用程序，原因：'[setValue：forUndefinedKey：]：此类不适用于键friendListTableView的键值编码。” *第一个抛出调用堆栈：（0 CoreFoundation 0x000000010d35fa75 exceptionPreprocess + 165 1 libobjc.A.dylib 0x000000010efeabb7 objc_exception_throw + 45 2 CoreFoundation 0x000000010d35f6b9-[NSException提高] + 9 3 Foundation 0x000000010d803d43-[NSObject（NSKeyValueFording）set： CoreFoundation 0x000000010d2a95e0-[NSArray makeObjectsPerformSelector：] + 224 5 UIKit 0x000000010dfec4ed-[UINib InstantiateWithOwner：options：] + 1506 6 UIKit 0x000000010de4aa88-[UIViewController _loadViewFromNibNamed：bundle：] + 242 7 UIKit 0View0000000b-0b0000004b-0de0000000b-0b000000de4b-0b000000de4b-0b000000de4b-0b000000de4b-0b000000de4b-0b000000de4b-0b000000de4b -00b-0b-0b000000de4b-0b000000de4b-0b000000de4b-0b000000de4b-0b-0b000000de4b-0b-0b000000de4b-0b-0b-0b000000de4b-0b-0b000000de4b-0b-0b-0b-0b000000de4b-0b-0b000000de4b-0b-0b-0b000000de4b-0b-0b -00b----- [UITableViewController loadView] + 76 9 UIKit 0x000000010de4b2e9-[UIViewController loadViewIfRequired] + 75 10 UIKit 0x000000010de4b77e-[UIViewController视图] + 27 11 UIKit 0x000000010e3eef4e-[_ UIFullscreenPresentationController _setPresentedViewControllersInPredetedViewController 0：-PredeedtedViewr：Presentwith26DeUItr：26 -65 oller：] + 105 13 UIKit 0x000000010de57531-[UIViewController _presentViewController：withAnimationController：completion：] + 1746 14 UIKit 0x000000010de59871 __62- [UIViewController presentViewController：animated：completion：] _ block_invoke + 132 15 UIKit 0x000000mdededede 9595：[tionViewaniController] + 229 16 ParseStarterProject 0x000000010c81c1c0 _TFC19ParseStarterProject14ViewController13viewDidAppearfS0_FSbT_ + 1488 17 ParseStarterProject 0x000000010c81c231 _TToFC19ParseStarterProject14ViewController13viewDidAppearfS0_FSbT_ + 49 18的UIKit 0x000000010de4f361 - [UIViewController中_setViewAppearState：isAnimating：] + 567 19的UIKit 0x000000010de4feab - [UIViewController中_executeAfterAppearanceBlock] + 52 20的UIKit 0x000000010dd48adb _applyBlockToCFArrayCopiedToStack + 314 21的UIKit 0x000000010dd48974 _afterCACommitHandler + 547 22 CoreFoundation 0x000000010d294507 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 23 23 CoreFoundation 0x000000010d294460 __CFRunLoopDoObservers + 368 24的CoreFoundation 0x000000010d28a293 __CFRunLoopRun + 1123 25的CoreFoundation 0x000000010d289bc6 CFRunLoopRunSpecific + 470 26 GraphicsServices 0x0000000110a99a58 GSEventRunModal + 161 27的UIKit 0x000000010dd25580 UIApplicationMain + 1282 28 ParseStarterProject 0x000000010c8203ae top_level_code + 78 29 ParseStarterProject 0x000000010c82048a主+ 42 30 libdyld.dylib 0x000000010f802145 START + 1）+的libc + abi.dylib：以类型为NSException（lldb）的未捕获异常终止

更新：修复错误，这些是我解析的类的屏幕快照，我的解析类为“用户” https://www.dropbox.com/s/6xp48v3yn0l2hje/Screen%20Shot%202015-06-03%20at%202.10.13%20PM。 png？dl = 0这是我当前用户在“朋友”列中的朋友列表https://www.dropbox.com/s/pd8mt8sf35u1m0v/Screen%20Shot%202015-06-03%20at%202.10.55%20PM.png ？dl = 0

Answer 1

PFUser.query仅查询User表。 看起来您真正要查询的是“ Friends”表或“ Messages”表。 不同的查询具有不同类型的对象以强制转换为对象，例如PFObject，PFUser ...如果要查询User表，则可以在下面找到工作代码：

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
    }
}

如果要查询其他表，则必须将PFUser.query更改为PFQuery。 我最近遇到了同样的问题。 您可以在这里找到我编写的示例代码