一个-ObserveValueForkeyPath：OfObject：更改：上下文：收到消息但未处理消息
https://stackoverflow.com/questions/4120539
-
29-09-2019 - |
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我对KVO是相对较新的，因此我很有可能违反了一些基本规则。我正在使用核心数据。
我的应用程序崩溃了以下消息：我无法理解的是，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”.
触发的所有事情都是：
[[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MeasorementDescriptor对象 - 并且两个都是NSManageBoct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）”）。在每个唯一的测量单位组合中，smuerementDeScriptors类似于单例。
测量值通过其他对象（模型对象和控制器对象）引用。 MeasurementPointer引用了MeasurementDeScriptor。许多对象有兴趣知道smayurmentPointer何时开始引用新/不同的MeasurementDeScriptor。例如，这样的更改可能会导致图形显示器的轴更改。或者，在上面的代码中，可能会导致仪表显示以显示不同的样本（来自选定的样本集）。
我认为基本问题是，一个CGimage正在收到一条无意的信息……不幸的是，这是间歇性的，因此我无法找到触发它的模式。
解决方案
您有一个被换取的对象，并且没有停止观察另一个对象。穿过你的所有 -addObserver... 呼叫并确保它们与 -removeObserver... 至少在 -dealloc 并且可能在 -viewDidUnload 取决于您的应用结构。
其他提示
当我发送了这个错误时，我看到了这个错误 observeValueForKeyPath 方法 super, ，我尚未注册为更改的观察者。 苹果文档 说“一定要调用超级阶级的实现[ observeValueForKeyPath] 如果实现它."
我的修复是改变：
- (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]) {
...
}
}
在Swift：
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) {
}
}
我意外地将目标传递成观察者（而不是自我），从而遇到了这个问题：
[self.someView addObserver:self.someView forKeyPath:@"key" options:0 context:nil];
错误消息对识别这一点根本没有帮助，因此，只要以为其他人也会做同样的事情，我就会张贴。
我遇到了同样的问题，但是就我而言，我正在观察不同的环境。然后，我将所有内容都放在相同的上下文中，崩溃消失了。我希望这可以帮助别人。
对我来说，我忘了添加 override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) 实际上观察到的键盘。
这是Swift版本的示例。将观察者添加到 viewDidLoad 并将它们删除 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")
}
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