ios之PFQuery:无法从解析数组中获取 objectId

我正在为社交墙制作类似的功能。 当 currentUser 执行此操作时，它会将消息中的 objectId 添加到 User 类中的数组列中:

func likeBtnClick(sender: AnyObject){ 
    let senderbutton:UIButton = sender as UIButton 
    println("current row is = \(senderbutton.tag)") 
 
    let tempObject:PFObject = ImageTimeLineData.objectAtIndex(senderbutton.tag) as PFObject 
    println("\(tempObject.objectId)") 
 
    PFUser.currentUser().addUniqueObject(tempObject.objectId, forKey: "liked") 
    PFUser.currentUser().saveInBackground() 
} 

这就是您将在“喜欢的”数组中获得的内容:["q6begjrFE4","s63ehjxFA1"]

这一切都很好。 现在我想从 cellForRowAtIndexPath 中的消息中检索喜欢的数量，并在按钮中显示喜欢的数量:

    ..... 
    let message:PFObject = self.ImageTimeLineData.objectAtIndex(indexPath!.row) as PFObject 
 
    ..... 
 
    var findLikes:PFQuery = PFUser.query() 
    findLikes.whereKey("liked", equalTo: message.objectForKey("objectId")) 
    findLikes.findObjectsInBackgroundWithBlock{ 
        (objects:[AnyObject]!, error:NSError!) -> Void in 
        if error == nil{ 
            let liked:NSArray = objects as NSArray 
            println(liked) 
            println(liked.count) 
            cell.likedButton.setTitle("\(liked.count)", forState: UIControlState.Normal) 
        } 
    } 
 
    ..... 
 
    cell.likedButton.tag = indexPath!.row 
    cell.likedButton.addTarget(self, action: "likeBtnClick:", forControlEvents: UIControlEvents.TouchUpInside) 
 
    return cell 

这将使应用程序崩溃，表示它无法对类型 null 进行比较查询。我已经设置了异常断点并来到这里:+[PFInternalUtils assertValidClassForQuery:]。它崩溃于此:findLikes.whereKey("liked", equalTo: message.objectForKey("objectId")) 行。

#0  0x01833a6b in objc_exception_throw () 
#1  0x01bae86d in +[NSException raise:format:] () 
#2  0x00197f30 in +[PFInternalUtils assertValidClassForQuery:] at /Users/nlutsenko/src/parse/ios-client/Parse/Internal/PFInternalUtils.m:368 
#3  0x001679d3 in -[PFQuery whereKey:equalTo:] at /Users/nlutsenko/src/parse/ios-client/Parse/PFQuery.m:195 
#4  0x000cce00 in TongerenApp.ImageTimeLineTableViewController.tableView (TongerenApp.ImageTimeLineTableViewController)(Swift.Optional<ObjectiveC.UITableView>, cellForRowAtIndexPath : Swift.Optional<ObjectiveC.NSIndexPath>) -> ObjectiveC.UITableViewCell at /Users/Dax/Desktop/TongerenApp/TongerenApp/ImageTimeLineTableViewController.swift:130 
#5  0x000cf143 in @objc TongerenApp.ImageTimeLineTableViewController.tableView (TongerenApp.ImageTimeLineTableViewController)(Swift.Optional<ObjectiveC.UITableView>, cellForRowAtIndexPath : Swift.Optional<ObjectiveC.NSIndexPath>) -> ObjectiveC.UITableViewCell () 
#6  0x022881bc in -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] () 
#7  0x0228829e in -[UITableView _createPreparedCellForGlobalRow:willDisplay:] () 
#8  0x02261a6b in -[UITableView _updateVisibleCellsNow:isRecursive:] () 
#9  0x0227c3d1 in -[UITableView layoutSubviews] () 
#10 0x021f1dd1 in -[UIView(CALayerDelegate) layoutSublayersOfLayer:] () 
#11 0x01849771 in -[NSObject performSelector:withObject:] () 
#12 0x0074628f in -[CALayer layoutSublayers] () 
#13 0x0073a115 in CA::Layer::layout_if_needed(CA::Transaction*) () 
#14 0x00739f70 in CA::Layer::layout_and_display_if_needed(CA::Transaction*) () 
#15 0x006983c6 in CA::Context::commit_transaction(CA::Transaction*) () 
#16 0x0069978c in CA::Transaction::commit() () 
#17 0x00699e58 in CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) () 
#18 0x01ad19de in __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ () 
#19 0x01ad1920 in __CFRunLoopDoObservers () 
#20 0x01ac735a in __CFRunLoopRun () 
#21 0x01ac6bcb in CFRunLoopRunSpecific () 
#22 0x01ac69fb in CFRunLoopRunInMode () 
#23 0x052da24f in GSEventRunModal () 
#24 0x052da08c in GSEventRun () 
#25 0x021668b6 in UIApplicationMain () 
#26 0x0010ff9e in top_level_code at /Users/Dax/Desktop/TongerenApp/TongerenApp/AppDelegate.swift:12 
#27 0x0011008b in main () 
#28 0x03885ac9 in start () 

找了下还是不太明白这是什么意思。似乎查询是错误的。如何访问“喜欢的”数组并进行比较？

请您参考如下方法:

我的第一个猜测是，问题是:

message.objectForKey("objectId") 

语法 objectForKey 适用于您创建的 PFObjects 的那些列，但 objectId 是由 Parse 创建的。因此，只需使用

message.objectId 

，因为 objectId 存储为 PFObject 的属性。