我是KVO的新手，因此很有可能违反一些基本规则。我正在使用核心数据。
我的应用程序崩溃并显示以下消息:我不明白的是，为什么CGImage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”.
触发此事件的所有原因是:
[[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-它们都是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)”)。在每个唯一的度量单位组合只有一个的情况下，MeasurementDescriptor类似于单例。
MeasurementPointers被其他对象(模型对象和 Controller 对象)引用。 MeasurementPointer引用MeasurementDescriptor。许多对象都想知道何时MeasurementPointer开始引用新的/不同的MeasurementDescriptor。例如，这种变化可能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屏显示不同的样本(来自一组选定的样本)。
我认为根本的问题是CGImage接收到了不适合它的消息...不幸的是，这是断断续续的，因此我无法找到触发它的模式。
最佳答案
您有一个已取消分配的对象，并且没有停止观察另一个对象。遍历所有-addObserver...调用，并确保至少与-removeObserver...以及可能取决于-dealloc的-viewDidUnload调用匹配，具体取决于您的应用程序结构。