我正在尝试使用从 iPhone 教程书中获得的 KVO 示例,但出现此异常
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '<UINavigationController: 0x139630>: An -observeValueForKeyPath:ofObject:change:context: message was received but not handled.
Key path: dataUpdated
Observed object: <FilterDetailsController: 0x1b9930>
Change: {
kind = 1;
}
Context: 0x0'
Call stack at first throw:
(
0 CoreFoundation 0x320d3987 __exceptionPreprocess + 114
1 libobjc.A.dylib 0x3271849d objc_exception_throw + 24
2 CoreFoundation 0x320d37c9 +[NSException raise:format:arguments:] + 68
3 CoreFoundation 0x320d3803 +[NSException raise:format:] + 34
4 Foundation 0x35c316e9 -[NSObject(NSKeyValueObserving) observeValueForKeyPath:ofObject:change:context:] + 60
5 Foundation 0x35bd4a3d NSKeyValueNotifyObserver + 216
6 Foundation 0x35bd46e5 NSKeyValueDidChange + 236
7 Foundation 0x35bcc3f5 -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:] + 76
8 Foundation 0x35c30d87 _NSSetObjectValueAndNotify + 98
9 Lucid Dreaming App 0x000108e3 -[FilterDetailsController adjustFilterDetails:] + 138
10 CoreFoundation 0x3207afed -[NSObject(NSObject) performSelector:withObject:withObject:] + 24
11 UIKit 0x323b3ea5 -[UIApplication sendAction:to:from:forEvent:] + 84
12 UIKit 0x323b3e45 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 32
13 UIKit 0x323b3e17 -[UIControl sendAction:to:forEvent:] + 38
14 UIKit 0x323b3b69 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 356
15 UIKit 0x323b43c7 -[UIControl touchesEnded:withEvent:] + 342
16 UIKit 0x323a9d4d -[UIWindow _sendTouchesForEvent:] + 368
17 UIKit 0x323a96c7 -[UIWindow sendEvent:] + 262
18 UIKit 0x3239499f -[UIApplication sendEvent:] + 298
19 UIKit 0x323942df _UIApplicationHandleEvent + 5090
20 GraphicsServices 0x35472f03 PurpleEventCallback + 666
21 CoreFoundation 0x320686ff __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 26
22 CoreFoundation 0x320686c3 __CFRunLoopDoSource1 + 166
23 CoreFoundation 0x3205af7d __CFRunLoopRun + 520
24 CoreFoundation 0x3205ac87 CFRunLoopRunSpecific + 230
25 CoreFoundation 0x3205ab8f CFRunLoopRunInMode + 58
26 GraphicsServices 0x354724ab GSEventRunModal + 114
27 GraphicsServices 0x35472557 GSEventRun + 62
28 UIKit 0x323c7d21 -[UIApplication _run] + 412
29 UIKit ...
我从
开始[advancedController addObserver:self.navigationController forKeyPath:@"dataUpdated" options:0 context:nil];
在 self.navigation Controller 中,我定义了观察方法:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"2 Observed change for: %@",keyPath);
// if (context == <#context#>) {
// <#code to be executed upon observing keypath#>
// } else {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
// }
}
在advancedController中我有一个NSNumber属性
@property(nonatomic,retain)NSNumber* dataUpdated;
当我按下按钮时,我希望观察者会开火。
- (IBAction)adjustFilterDetails:(id)sender {
self.dataUpdated = [NSNumber numberWithInt:[self.dataUpdated intValue]+1];
}
我是否需要实现某些协议(protocol)或明确声明我将更新该值?我读到 NSKeyValueObserving 是一个“非正式”协议(protocol)。感谢您的帮助!
我已经找到了自己问题的答案。我在 ViewController 中定义了 KVO 协议(protocol)方法,但是,我不小心为 View Controller 注册了导航 Controller 来观察该值。通过获取 View Controller 可以找到正确的对象,如下所示:
[advancedController addObserver:(RootViewController*)self.navigationController. topViewController forKeyPath:@"dataUpdated" options:0 context:nil];
最佳答案
您的问题是对 super
的调用。对于您自己观察到的属性,您不应将此方法传递给 super
。您注释掉了可以帮助您完成此操作的代码。
一个可能的正确观察是(注意上下文):
[advancedController addObserver:self.navigationController forKeyPath:@"dataUpdated" options:0 context:self];
那么正确的观察者是:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if (context == self) {
NSLog(@"2 Observed change for: %@",keyPath);
} else {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}
Dave Dribin 在 Proper Key-Value Observer Usage 中提供了另一种正确使用上下文
的方法,以及为什么需要这种方法的背景故事。 .
关于ios - 使用 KVO 时出现 NSInternalInconsistencyException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7599979/