異常的未經處理過的觀察者

Question

我使用下面的代碼添加觀察員：

[self.priorityQueue addObserver:self forKeyPath:@"operations" options:options context:NULL]; 

，並觀察方法定義爲：

-(void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object 
        change:(NSDictionary *)change context:(void *)context 
{ 
    if ([object isKindOfClass:[NSOperationQueue class]] && [keyPath isEqualToString:@"operations"]) { 
     //calling my method 
    } 
    else {  
     [super observeValueForKeyPath:keyPath ofObject:object 
         change:change context:context]; 
    } 
} 

，但我得到以下錯誤：

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: ' ( Context: 0x0, Property: 0x110bf60>): An -observeValueForKeyPath:ofObject:change:context: message was received but not handled. Key path: operations Observed object: {name = 'NSOperationQueue 0x11213c0'} Change:

請告訴我，如果我在觀察者方法中犯了一些錯誤。

感謝，

Answer 1

NSObject的不執行該功能 - 如果要擴展NSObject的不調用超。

從蘋果文檔：

Be sure to call the superclass's implementation *if it implements it*. 
NSObject does not implement the method. 

https://developer.apple.com/library/ios/documentation/cocoa/conceptual/KeyValueObserving/Articles/KVOBasics.html