NSOperationQueue 在 IOS 中崩溃 [英] NSOperationQueue is crashing in IOS

问题描述

我有一个使用 NSOperationQueue 在后台下载图像的项目.到目前为止，它一直在 IOS 4.3 的设备上运行.但是，如果我使用基础 sdk 4.3 或 5 构建应用程序并在使用 IOS5 的设备上运行应用程序，应用程序就会崩溃.当应用程序启动时，它会将 NSOperation 对象添加到下载图像的队列中.如果在这之间我按下后退按钮，我会取消 NSOperation 并且它崩溃并在控制台上显示以下跟踪:

<前>#0 0x004727b7 在 ____NSOQSchedule_block_invoke_0 ()#1 0x026a5618 在_dispatch_call_block_and_release()#2 0x026a7a10 在_dispatch_worker_thread2 ()#3 0x974bb781 in _pthread_wqthread()#4 0x974bb5c6 在 start_wqthread ()

并打印ResourceLoadOperation isFinished = YES 而不被它所在的队列启动"如果我评论取消方法调用，应用程序不会崩溃.IOS5 的 NSOperation 更改是否有任何更新?

解决方案

我在针对 iOS 5 构建时遇到了同样的问题.我最终创建了一个名为 operationStarted 的标志，它是 NO 默认情况下，当调用 start 方法时，我切换到 YES.然后在我的 finish 方法(我在其中生成 KVO 通知)中，我在触发通知之前检查了标志的值.

标志定义如下所示:

@property (nonatomic, assign, getter=isOperationStarted) BOOL operationStarted;

start 方法:

- (void)start {[self setOperationStarted:YES];...}

我的finish方法，在操作完成或取消时调用:

- (void)finish {if (![self isOperationStarted]) 返回；[self willChangeValueForKey:@"isExecuting"];执行=否；[self didChangeValueForKey:@"isExecuting"];[self willChangeValueForKey:@"isFinished"];完成 = 是;[self didChangeValueForKey:@"isFinished"];}

这最终为我解决了问题.希望能帮到别人.

I have a project which downloads images in background using NSOperationQueue. It was working until now on devices with IOS 4.3. However if I build the app with base sdk 4.3 or with 5 and run the app on device with IOS5, the app crashes. When app is launched, it adds NSOperation objects into queue for downloading the images. If in between I press back button, I cancel the NSOperation and it crashes and displays following trace on console:

#0  0x004727b7 in ____NSOQSchedule_block_invoke_0 ()
#1  0x026a5618 in _dispatch_call_block_and_release ()
#2  0x026a7a10 in _dispatch_worker_thread2 ()
#3  0x974bb781 in _pthread_wqthread ()
#4  0x974bb5c6 in start_wqthread ()

and prints "ResourceLoadOperation isFinished = YES without being started by the queue it is in" If I comment the cancel method call, app doesnot crash. Is there any updates on the NSOperation changes for IOS5?

解决方案

I had this same problem when building against iOS 5. I ended up creating a flag named operationStarted that was NO by default and I toggled to YES when the start method was called. Then in my finish method (where I generate the KVO notifications), I checked the value of the flag before firing the notifications.

The flag definition looks like this:

@property (nonatomic, assign, getter=isOperationStarted) BOOL operationStarted;

The start method:

- (void)start {
    [self setOperationStarted:YES];
    ...
}

My finish method which is called when the operation is complete or cancelled:

- (void)finish {    
    if (![self isOperationStarted]) return;

    [self willChangeValueForKey:@"isExecuting"];
    executing = NO;
    [self didChangeValueForKey:@"isExecuting"];

    [self willChangeValueForKey:@"isFinished"];
    finished = YES;
    [self didChangeValueForKey:@"isFinished"];
}

That ended up resolving the issue for me. Hope it helps someone else.

这篇关于NSOperationQueue 在 IOS 中崩溃的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！