iphone - Crashing with ASIHTTPRequest and NSOperationQueue when cancelling operations

Question

I'm having a really hard time when trying to cancel requests in an NSOperationQueue.

Before deallocating my 'engine' object, I call a cancelOperations method to cancel everything in the queue, so this will include in flight ASIHTTPRequests and queued ones... e.g.

Engine.m

-(void)getContent {
    if (![self queue]) {
        [self setQueue:[[[NSOperationQueue alloc] init] autorelease]];
    }

    NSURL *url = [NSURL URLWithString:@"http://allseeing-i.com"];
    ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
    [request setDelegate:self];
    [request setDidFinishSelector:@selector(requestDone:)];
    [[self queue] addOperation:request]; //queue is an NSOperationQueue
}

-(void)requestDone:(ASIHTTPRequest)*request {

    // Do something with request
}

-(void)cancelOperations {
    [self.queue cancelAllOperations];
    [self.queue waitUntilAllOperationsAreFinished];
}

-(void)dealloc {
    [super dealloc];
}

Now, In my engine I have a number of getContent type methods, so my queue has different request objects in it. The flow when using an Engine object is:

1) Open View Controller - view did load - alloc and init Engine object
2) // Call various getContent style methods to queue up some operations
3) Upon view exit, call [engine cancelOperations]; in order to (a) Stop any network requests in flight, and to also empty the queue
4) Deallocate the view, and with that the engine: [engine release];

This works fine if all requests have finished in the queue (as it's empty), however if I cancelOperations whilst a request is active, the application crashes with a EXC_BAD_ACCESS error... but AFTER the engine is deallocated successfully...

Any ideas why this would be?

--EDIT-- Adding Backtrace for error:

Exception Type:  EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x00000000b0000000
Crashed Thread:  0  Dispatch queue: com.apple.main-thread

Application Specific Information:
objc_msgSend() selector name: respondsToSelector:
iPhone Simulator 225, iPhone OS 4.1 (iPhone 4/8B117)

Thread 0 Crashed:  Dispatch queue: com.apple.main-thread
0   libobjc.A.dylib                 0x02cb5907 objc_msgSend + 27
1   CoreFoundation                  0x02ac95cd __invoking___ + 29
2   CoreFoundation                  0x02ac94a1 -[NSInvocation invoke] + 145
3   Foundation                      0x0015a3ca __NSThreadPerformPerform + 251
4   CoreFoundation                  0x02b39faf __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
5   CoreFoundation                  0x02a9839b __CFRunLoopDoSources0 + 571
6   CoreFoundation                  0x02a97896 __CFRunLoopRun + 470
7   CoreFoundation                  0x02a97350 CFRunLoopRunSpecific + 208
8   CoreFoundation                  0x02a97271 CFRunLoopRunInMode + 97
9   GraphicsServices                0x0320c00c GSEventRunModal + 217
10  GraphicsServices                0x0320c0d1 GSEventRun + 115
11  UIKit                           0x003e9af2 UIApplicationMain + 1160
12  Clicky                          0x000027d4 main + 102 (main.m:14)
13  Clicky                          0x00002765 start + 53

Thread 1:  Dispatch queue: com.apple.libdispatch-manager
0   libSystem.B.dylib               0x97cfe942 kevent + 10
1   libSystem.B.dylib               0x97cff05c _dispatch_mgr_invoke + 215
2   libSystem.B.dylib               0x97cfe519 _dispatch_queue_invoke + 163
3   libSystem.B.dylib               0x97cfe2be _dispatch_worker_thread2 + 240
4   libSystem.B.dylib               0x97cfdd41 _pthread_wqthread + 390
5   libSystem.B.dylib               0x97cfdb86 start_wqthread + 30

Thread 2:
0   libSystem.B.dylib               0x97cfd9d2 __workq_kernreturn + 10
1   libSystem.B.dylib               0x97cfdf68 _pthread_wqthread + 941
2   libSystem.B.dylib               0x97cfdb86 start_wqthread + 30

Thread 3:  WebThread
0   libSystem.B.dylib               0x97cd80fa mach_msg_trap + 10
1   libSystem.B.dylib               0x97cd8867 mach_msg + 68
2   CoreFoundation                  0x02b3a436 __CFRunLoopServiceMachPort + 150
3   CoreFoundation                  0x02a97984 __CFRunLoopRun + 708
4   CoreFoundation                  0x02a97350 CFRunLoopRunSpecific + 208
5   CoreFoundation                  0x02a97271 CFRunLoopRunInMode + 97
6   WebCore                         0x034093a3 RunWebThread(void*) + 483
7   libSystem.B.dylib               0x97d0581d _pthread_start + 345
8   libSystem.B.dylib               0x97d056a2 thread_start + 34

Thread 4:
0   libSystem.B.dylib               0x97cfd9d2 __workq_kernreturn + 10
1   libSystem.B.dylib               0x97cfdf68 _pthread_wqthread + 941
2   libSystem.B.dylib               0x97cfdb86 start_wqthread + 30

Thread 5:
0   libSystem.B.dylib               0x97cd80fa mach_msg_trap + 10
1   libSystem.B.dylib               0x97cd8867 mach_msg + 68
2   CoreFoundation                  0x02b3a436 __CFRunLoopServiceMachPort + 150
3   CoreFoundation                  0x02a97984 __CFRunLoopRun + 708
4   CoreFoundation                  0x02a97350 CFRunLoopRunSpecific + 208
5   CoreFoundation                  0x02a9a614 CFRunLoopRun + 84
6   Clicky                          0x0001fdb7 +[ASIHTTPRequest runRequests] + 167 (ASIHTTPRequest.m:4093)
7   Foundation                      0x0014576c -[NSThread main] + 81
8   Foundation                      0x001456f8 __NSThread__main__ + 1387
9   libSystem.B.dylib               0x97d0581d _pthread_start + 345
10  libSystem.B.dylib               0x97d056a2 thread_start + 34

Thread 6:
0   libSystem.B.dylib               0x97cd80fa mach_msg_trap + 10
1   libSystem.B.dylib               0x97cd8867 mach_msg + 68
2   CoreFoundation                  0x02b3a436 __CFRunLoopServiceMachPort + 150
3   CoreFoundation                  0x02a97984 __CFRunLoopRun + 708
4   CoreFoundation                  0x02a97350 CFRunLoopRunSpecific + 208
5   CoreFoundation                  0x02a97271 CFRunLoopRunInMode + 97
6   Foundation                      0x0017ab86 +[NSURLConnection(NSURLConnectionReallyInternal) _resourceLoadLoop:] + 398
7   Foundation                      0x0014576c -[NSThread main] + 81
8   Foundation                      0x001456f8 __NSThread__main__ + 1387
9   libSystem.B.dylib               0x97d0581d _pthread_start + 345
10  libSystem.B.dylib               0x97d056a2 thread_start + 34

Thread 7:
0   libSystem.B.dylib               0x97cf7086 select$DARWIN_EXTSN + 10
1   CoreFoundation                  0x02acbb5e __CFSocketManager + 798
2   libSystem.B.dylib               0x97d0581d _pthread_start + 345
3   libSystem.B.dylib               0x97d056a2 thread_start + 34

Thread 8:
0   libSystem.B.dylib               0x97cfd9d2 __workq_kernreturn + 10
1   libSystem.B.dylib               0x97cfdf68 _pthread_wqthread + 941
2   libSystem.B.dylib               0x97cfdb86 start_wqthread + 30

Thread 0 crashed with X86 Thread State (32-bit):
  eax: 0x06641500  ebx: 0x000143f3  ecx: 0x0008e1c8  edx: 0x06606075
  edi: 0xb0000000  esi: 0x066554c4  ebp: 0xbfffdef8  esp: 0xbfffdec4
   ss: 0x0000001f  efl: 0x00010206  eip: 0x02cb5907   cs: 0x00000017
   ds: 0x0000001f   es: 0x0000001f   fs: 0x00000000   gs: 0x00000037
  cr2: 0xb0000000

score 4 · Accepted Answer

您没有在 dealloc 中释放您的操作队列...

一个怀疑是委托模式：

[request setDelegate:self];

如果self对象被销毁，而请求没有被销毁，当请求“完成”时，它会尝试通知内存中的一些垃圾，从而崩溃。

更新：要修补此问题，请在取消之前添加此代码：

for (ASIHTTPRequest *request in queue.operations) 
{ 
    [request setDelegate: nil]; 
    [request setDidFinishSelector: nil];
}

score 4 · Accepted Answer

我认为 jv42 关于原因是正确的。但是，有一个方便的帮手来清理代表......

-(void)dealloc {
    for (ASIHTTPRequest *request in queue.operations) { 
     [request clearDelegatesAndCancel]; 
    }
    [queue release];
    [super dealloc];
}

有没有人为此找到一种更快的方法......也许不涉及循环请求的方法？

score 0 · Accepted Answer

在运行具有多个请求的 ASINetworkQueue 时，我遇到了同样的情况。

我删除了队列的 dealloc 释放和自动释放。然后我应用了 Leah 的绝妙建议来循环到 nil 代表。然后我将队列的发布放在 queueRequestFinished 委托中，它解决了我的问题！

bulkQueue = [[ASINetworkQueue alloc] init];

[bulkQueue setQueueDidFinishSelector:@selector(queueRequestFinished:)];

-(void)queueRequestFinished:(ASINetworkQueue *)queue
{
    for (ASIHTTPRequest *request in queue.operations) 
    { 
        [request setDelegate: nil]; 
        [request setDidFinishSelector: nil];
    }

}

希望这可以帮助某人！:-)

score 0 · Accepted Answer

确保您正在运行最新的 git 版本的 ASIHTTPRequest - v1.7 包含几个竞争条件，这些条件会在取消请求时导致崩溃。

iphone - Crashing with ASIHTTPRequest and NSOperationQueue when cancelling operations

4 回答 4

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