Objective c 连接到NSOperationQueue operationsCount的observeValueForKeyPath中崩溃

我在UIView子类中有

UITextView日志视图

（尝试了

原子的

和

非原子的

）和

NSOperationQueue uploadQueue

属性。 我在我的

NSOperationQueue

属性的

operationcount

上添加了KVO，如下所示：

[[self uploadQueue] addObserver:self
            forKeyPath:@"operationCount" 
               options:(NSKeyValueObservingOptionNew |
                        NSKeyValueObservingOptionOld)
               context:NULL];

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    if ([object isKindOfClass: [NSOperationQueue class]]) {
        NSLog(@"Keypath is: %@ change dictionary is: %@", keyPath, change);
        NSInteger testnew = [[change objectForKey: @"new"] integerValue];
        NSInteger testold = [[change objectForKey: @"old"] integerValue];
        if (testnew > testold) {
            [[self logView] setText: [NSString stringWithFormat: @"Uploading %d files", testnew]];
            objc_setAssociatedObject([self logView], @"max_value_of_uploads", [change objectForKey: @"new"], OBJC_ASSOCIATION_COPY);
        } else {
            NSInteger value = [objc_getAssociatedObject([self logView], @"max_value_of_uploads") integerValue]; 
            [[self logView] setText: [NSString stringWithFormat: @"Uploaded %d of %d files", testnew, value]];
        }
    }
}

bool _WebTryThreadLock(bool), 0x10617fb0: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...
1   WebThreadLock
2   -[UITextView setText:]
3   -[SincViewController observeValueForKeyPath:ofObject:change:context:]
4   NSKeyValueNotifyObserver
5   NSKeyValueDidChange
6   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:key:key:usingBlock:]
7   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:usingBlock:]
8   ____NSOQDelayedFinishOperations_block_invoke_0
9   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:key:key:usingBlock:]
10  -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:usingBlock:]
11  __NSOQDelayedFinishOperations
12  _dispatch_after_timer_callback
13  _dispatch_source_invoke
14  _dispatch_queue_invoke
15  _dispatch_worker_thread2
16  _pthread_wqthread
17  start_wqthread

观察者函数如下所示：

[[self uploadQueue] addObserver:self
            forKeyPath:@"operationCount" 
               options:(NSKeyValueObservingOptionNew |
                        NSKeyValueObservingOptionOld)
               context:NULL];

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    if ([object isKindOfClass: [NSOperationQueue class]]) {
        NSLog(@"Keypath is: %@ change dictionary is: %@", keyPath, change);
        NSInteger testnew = [[change objectForKey: @"new"] integerValue];
        NSInteger testold = [[change objectForKey: @"old"] integerValue];
        if (testnew > testold) {
            [[self logView] setText: [NSString stringWithFormat: @"Uploading %d files", testnew]];
            objc_setAssociatedObject([self logView], @"max_value_of_uploads", [change objectForKey: @"new"], OBJC_ASSOCIATION_COPY);
        } else {
            NSInteger value = [objc_getAssociatedObject([self logView], @"max_value_of_uploads") integerValue]; 
            [[self logView] setText: [NSString stringWithFormat: @"Uploaded %d of %d files", testnew, value]];
        }
    }
}

bool _WebTryThreadLock(bool), 0x10617fb0: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...
1   WebThreadLock
2   -[UITextView setText:]
3   -[SincViewController observeValueForKeyPath:ofObject:change:context:]
4   NSKeyValueNotifyObserver
5   NSKeyValueDidChange
6   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:key:key:usingBlock:]
7   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:usingBlock:]
8   ____NSOQDelayedFinishOperations_block_invoke_0
9   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:key:key:usingBlock:]
10  -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:usingBlock:]
11  __NSOQDelayedFinishOperations
12  _dispatch_after_timer_callback
13  _dispatch_source_invoke
14  _dispatch_queue_invoke
15  _dispatch_worker_thread2
16  _pthread_wqthread
17  start_wqthread

uploadQueue

填充的工作原理如下：

   ...
   NSDictionary *iter;
        NSEnumerator *enumerator = [objects objectEnumerator];
        while (iter = [enumerator nextObject]) {
            Uploader *op = [[Uploader alloc] initWithFileName: [iter objectForKey: @"fileName"] 
                                                             FileID: [[iter objectForKey: @"fileID"] integerValue] 
                                                       AndSessionID: [self sess]];
            //Uploader *op = [[Uploader alloc] init];
            [[self uploadQueue] addOperation: op];
   ...

如果没有

if-else

block，一切正常：我得到了关于队列中操作数的NSLog消息，这些操作数正常，等等。 但是有了

if-else

块，我得到了崩溃，它看起来像这样：

[[self uploadQueue] addObserver:self
            forKeyPath:@"operationCount" 
               options:(NSKeyValueObservingOptionNew |
                        NSKeyValueObservingOptionOld)
               context:NULL];

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    if ([object isKindOfClass: [NSOperationQueue class]]) {
        NSLog(@"Keypath is: %@ change dictionary is: %@", keyPath, change);
        NSInteger testnew = [[change objectForKey: @"new"] integerValue];
        NSInteger testold = [[change objectForKey: @"old"] integerValue];
        if (testnew > testold) {
            [[self logView] setText: [NSString stringWithFormat: @"Uploading %d files", testnew]];
            objc_setAssociatedObject([self logView], @"max_value_of_uploads", [change objectForKey: @"new"], OBJC_ASSOCIATION_COPY);
        } else {
            NSInteger value = [objc_getAssociatedObject([self logView], @"max_value_of_uploads") integerValue]; 
            [[self logView] setText: [NSString stringWithFormat: @"Uploaded %d of %d files", testnew, value]];
        }
    }
}

bool _WebTryThreadLock(bool), 0x10617fb0: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now...
1   WebThreadLock
2   -[UITextView setText:]
3   -[SincViewController observeValueForKeyPath:ofObject:change:context:]
4   NSKeyValueNotifyObserver
5   NSKeyValueDidChange
6   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:key:key:usingBlock:]
7   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:usingBlock:]
8   ____NSOQDelayedFinishOperations_block_invoke_0
9   -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:key:key:usingBlock:]
10  -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:usingBlock:]
11  __NSOQDelayedFinishOperations
12  _dispatch_after_timer_callback
13  _dispatch_source_invoke
14  _dispatch_queue_invoke
15  _dispatch_worker_thread2
16  _pthread_wqthread
17  start_wqthread

它在

else

块中崩溃。 此外，我没有看到我的日志视图有任何变化。 感谢您以后的帮助和回复

---

更新：

在设置保存的文本时执行selectoronmainthread

。

我建议您在此处使用委托模式。您似乎将非常先进的技术与一些松散的代码混合在一起，这可能会很快导致问题。例如，我认为您不需要关联对象

---

发生错误的原因是您正在从后台线程访问UI。您应该将UI调用（setText:）包装在performSelectorOnMainThread:内，并使用Object:waitUntilDone:或一个块。

更新UI时，请确保您处于主线程中。可能的解决办法如下：

dispatch_async(dispatch_get_main_queue(), ^{
    if (testnew > testold) {
        [[self logView] setText: [NSString stringWithFormat: @"Uploading %d files", testnew]];
        objc_setAssociatedObject([self logView], @"max_value_of_uploads", [change objectForKey: @"new"], OBJC_ASSOCIATION_COPY);
    } else {
        NSInteger value = [objc_getAssociatedObject([self logView], @"max_value_of_uploads") integerValue]; 
        [[self logView] setText: [NSString stringWithFormat: @"Uploaded %d of %d files", testnew, value]];
    }
}); 

请注意，使用

dispatch\u async

或

dispatch\u sync

取决于所需的实现，但在后一种情况下，除非检查所处的线程，否则可能会出现死锁

另见： 有人建议将UI代码移动到单独的方法：

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
  [self performSelectorOnMainThread:@selector(dataLoadingFinished:) withObject:nil waitUntilDone:YES];
}

---

。。这是一个很好的替代路线。

请看：这就是写错的地方，是的。但除了主线程之外，我并没有在任何线程中使用观察器函数。我认为问题在于KVO的内部机制，也许它使用了额外的线程？无论如何，

performSelectorOnMainThread

在设置我保存的文本时。无论在哪个线程中发生更改，都将调用观察者。您使用的是NSOperationQueue，所以是的，它将在后台。但我无法获取它。NSOperation实例从队列中退出后发生的更改。NSOperationQueue就是这样，它“存在”在主线程中。我的意思是，事件显然发生在所谓的后台线程中，但它本身的更改必须发生在主线程中。我错在哪里？谢谢。阅读链接的答案。苹果甚至告诉你不要这样做。我读过。但除了相信我，我想了解他们。