32

我对 KVO 比较陌生，所以我很有可能违反了一些基本规则。我正在使用核心数据。

我的应用程序崩溃并显示以下消息：我不明白为什么 CGImage 会参与观察在 MeasurementPointer 对象上设置的值。

        *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '<CGImage 0x276fc0>: An -observeValueForKeyPath:ofObject:change:context: message was received but not handled.
Key path: measurementDescriptor
Observed object: <MeasurementPointer: 0x8201640> (entity: MeasurementPointer; id: 0x8200410 <x-coredata://EBEE0687-D67D-4B03-8C95-F4C60CFDC20F/MeasurementPointer/p75> ; data: {
    measurementDescriptor = "0x260fd0 <x-coredata://EBEE0687-D67D-4B03-8C95-F4C60CFDC20F/MeasurementDescriptor/p22>";
})
Change: {
    kind = 1;
    new = "<MeasurementDescriptor: 0x262530> (entity: MeasurementDescriptor; id: 0x260fd0 <x-coredata://EBEE0687-D67D-4B03-8C95-F4C60CFDC20F/MeasurementDescriptor/p22> ; data: {\n    measurementName = Temperature;\n    measurementUnits = \"\\U00b0C\";\n    sortString = nil;\n})";
}
Context: 0x0'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x30897ed3 __exceptionPreprocess + 114
    1   libobjc.A.dylib                     0x3002f811 objc_exception_throw + 24
    2   CoreFoundation                      0x30897d15 +[NSException raise:format:arguments:] + 68
    3   CoreFoundation                      0x30897d4f +[NSException raise:format:] + 34
    4   Foundation                          0x34a13779 -[NSObject(NSKeyValueObserving) observeValueForKeyPath:ofObject:change:context:] + 60
    5   Foundation                          0x349b6acd NSKeyValueNotifyObserver + 216
    6   Foundation                          0x349b6775 NSKeyValueDidChange + 236
    7   Foundation                          0x349ae489 -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:] + 76
    8   CoreData                            0x3165b577 _PF_ManagedObject_DidChangeValueForKeyIndex + 102
    9   CoreData                            0x3165ac51 _sharedIMPL_setvfk_core + 184
    10  CoreData                            0x3165dc83 _svfk_0 + 10
    11  SPARKvue                            0x000479f1 -[MeasurementViewController doneAction:] + 152
    12  CoreFoundation                      0x3083f719 -[NSObject(NSObject) performSelector:withObject:withObject:] + 24
    13  UIKit                               0x31eb1141 -[UIApplication sendAction:to:from:forEvent:] + 84
    14  UIKit                               0x31f08315 -[UIBarButtonItem(UIInternal) _sendAction:withEvent:] + 92
    15  CoreFoundation                      0x3083f719 -[NSObject(NSObject) performSelector:withObject:withObject:] + 24
    16  UIKit                               0x31eb1141 -[UIApplication sendAction:to:from:forEvent:] + 84
    17  UIKit                               0x31eb10e1 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 32
    18  UIKit                               0x31eb10b3 -[UIControl sendAction:to:forEvent:] + 38
    19  UIKit                               0x31eb0e05 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 356
    20  UIKit                               0x31eb1453 -[UIControl touchesEnded:withEvent:] + 342
    21  UIKit                               0x31eafddd -[UIWindow _sendTouchesForEvent:] + 368
    22  UIKit                               0x31eaf757 -[UIWindow sendEvent:] + 262
    23  UIKit                               0x31eaa9ff -[UIApplication sendEvent:] + 298
    24  UIKit                               0x31eaa337 _UIApplicationHandleEvent + 5110
    25  GraphicsServices                    0x31e4504b PurpleEventCallback + 666
    26  CoreFoundation                      0x3082cce3 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 26
    27  CoreFoundation                      0x3082cca7 __CFRunLoopDoSource1 + 166
    28  CoreFoundation                      0x3081f56d __CFRunLoopRun + 520
    29  CoreFoundation                      0x3081f277 CFRunLoopRunSpecific + 230
    30  CoreFoundation                      0x3081f17f CFRunLoopRunInMode + 58
    31  GraphicsServices                    0x31e445f3 GSEventRunModal + 114
    32  GraphicsServices                    0x31e4469f GSEventRun + 62
    33  UIKit                               0x31e51123 -[UIApplication _run] + 402
    34  UIKit                               0x31e4f12f UIApplicationMain + 670
    35  SPARKvue                            0x000031ff main + 70
    36  SPARKvue                            0x000031b4 start + 40
)
terminate called after throwing an instance of 'NSException'
Program received signal:  “SIGABRT”.

触发此事件的所有情况是：

[[self measurementPointer] setMeasurementDescriptor:descriptor];

鉴于这种，

[[meterDisplay measurementPointer] addObserver:self 
            forKeyPath:@"measurementDescriptor"
            options:NSKeyValueObservingOptionNew
            context:nil];

基本上，MeasurementPointer 对象指向 MeasurementDescriptor 对象 - 两者都是 NSManagedObject 子类。MeasurementDescriptor 对象描述了特定的“测量”和“单位”组合（例如，“温度 (°C)”或“风速 (mph)”）。MeasurementDescriptors 类似于单例，每个唯一的测量单位组合只有一个。

MeasurementPointers 被其他对象引用——包括模型对象和控制器对象。一个MeasurementPointer 引用一个MeasurementDescriptor。许多对象都想知道MeasurementPointer 何时开始引用新的/不同的MeasurementDescriptor。例如，这种变化可能会导致图形显示的轴发生变化。或者，在上面的代码中，可能会导致仪表显示显示不同的样本（来自选定的样本集）。

我认为根本问题是 CGImage 正在接收不适合它的消息......不幸的是，这是间歇性的，所以我无法找到触发它的模式。

4

5 回答 5

42

你有一个对象被释放并且没有停止观察另一个对象。遍历所有-addObserver...调用，并确保它们-removeObserver...至少与调用匹配，-dealloc并且可能在-viewDidUnload取决于您的应用程序结构中。

于 2010-11-09T14:13:16.560 回答
10

当我将observeValueForKeyPath方法发送到时，我看到了这个错误super，我没有注册为更改的观察者。Apple 文档说“如果实现它，请务必调用超类的实现 [of observeValueForKeyPath] 。”

我的解决办法是改变：

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context {
  if ([keyPath isEqualToString:kPropertyThatChanges]) {
    ...
  }
  [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}

到：

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context {
  if ([keyPath isEqualToString:kPropertyThatChanges]) {
    ...
  }
}

迅速：

func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if (keyPath == kPropertyThatChanges) {
    }
    super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
}
To:
func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if (keyPath == kPropertyThatChanges) {
    }
}
于 2015-04-22T16:10:57.150 回答
3

我不小心将目标作为观察者（而不是自我）传递给了这个问题，如下所示：

[self.someView addObserver:self.someView forKeyPath:@"key" options:0 context:nil];

该错误消息对于识别这一点根本没有帮助，所以只是想我会发布以防其他人做同样的事情。

于 2014-03-17T17:26:12.650 回答
1

我遇到了同样的问题，但就我而言，我观察的是不同的背景。然后我将所有内容放在相同的上下文中，崩溃就消失了。我希望这可以帮助别人。

于 2012-06-29T18:18:42.600 回答
1

对我来说，我忘了添加override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?)实际上对 keyPath 进行观察的操作。

这是 Swift 版本的示例。在 中添加观察者viewDidLoad并删除它们deinit：

lazy var firstNameTextField: UITextField = {
    let textField = UITextField()
    // configure your textField
    return textField
}()

lazy var lastNameTextField: UITextField = {
    let textField = UITextField()
    // configure your textField
    return textField
}()

override func viewDidLoad() {
    super.viewDidLoad()

    // 1. add your observers here
    firstNameTextField.addObserver(self, forKeyPath: "text", options: [.old, .new], context: nil)
    lastNameTextField.addObserver(self, forKeyPath: "text", options: [.old, .new], context: nil)
}

// 2. ***IMPORTANT you must add this function or it will crash***
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {

    if keyPath == "text" {
        print("do something when the textField's text your observing changes")
    }
}

 // 3. remove them in deinit
deinit {
    firstNameTextField.removeObserver(self, forKeyPath: "text", context: nil)
    lastNameTextField.removeObserver(self, forKeyPath: "text", context: nil)
    print("DEINIT")
}
于 2019-04-12T17:59:25.647 回答