NSBlockOperation EXC_BAD_ACCESS
NSBlockOperation EXC_BAD_ACCESS
我创建了一个实现了一些方法的 class。这些方法由另一个 class 调用,并通过 NSBlockOperation 进行管理。
我的 NSBlockOperation 工作正常,我在尝试计算变量时遇到问题:
EXC_BAD_ACCESS
我在互联网上做了很多研究,this 是最接近我的问题的。我试着像 sugerito 那样做,但你遇到了同样的问题。
你有什么建议吗?
编辑:
这是堆栈跟踪:
2015-05-09 15:24:45.976 OutParameters[12326:743087] Stack trace : (
0 OutParameters 0x000000010e5d6602 -[ListOperation _method1:] + 194
1 OutParameters 0x000000010e5d646f __25-[ListOperation method1:]_block_invoke + 95
2 Foundation 0x000000010e74257f __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__ + 7
3 Foundation 0x000000010e6830b2 -[NSBlockOperation main] + 98
4 Foundation 0x000000010e665774 -[__NSOperationInternal _start:] + 645
5 Foundation 0x000000010e665383 __NSOQSchedule_f + 184
6 libdispatch.dylib 0x00000001113f4614 _dispatch_client_callout + 8
7 libdispatch.dylib 0x00000001113db6a7 _dispatch_queue_drain + 2176
8 libdispatch.dylib 0x00000001113dacc0 _dispatch_queue_invoke + 235
9 libdispatch.dylib 0x00000001113de3b9 _dispatch_root_queue_drain + 1359
10 libdispatch.dylib 0x00000001113dfb17 _dispatch_worker_thread3 + 111
11 libsystem_pthread.dylib 0x0000000111761637 _pthread_wqthread + 729
12 libsystem_pthread.dylib 0x000000011175f40d start_wqthread + 13
)
修改后的代码:
- (IBAction)testCallMethod:(id)sender {
NSString * output;
[self.listOperationObj method1:&output];
NSLog(@"Output: %@", output);
}
和
@interface ListOperation : NSObject
-(void)method1:(NSString**)output;
@end
#define MAX_OPERATIONS 10
//define a log-level
static int logLevel = CSLOG_LEVEL_INFO;
@interface ListOperation ()
// Tail used to synchronize the methods
@property NSOperationQueue *queue;
@end
#pragma mark - Public methods
@implementation ListOperation
- (id)init {
self = [super init];
if(self) {
_queue = [NSOperationQueue new];
if(_queue) {
[_queue setMaxConcurrentOperationCount:1];
}else {
NSLog(@"TokenMgr creation failed: error creating operation queue");
self = nil;
}
}
return self;
}
-(void)method1:(NSString *__autoreleasing *)output{
LOGFSTART
if([self _isQueueFull] == FALSE) {
WEAK
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
STRONG
[strongSelf _method1:output];
}];
[self.queue addOperation:operation];
[operation waitUntilFinished];
}
else {
LOGE(@"TokenMgr's queue is full, aborting operation");
}
LOGFEND
}
#pragma mark - private methods
-(void)_method1:(NSString *__autoreleasing *)output{
std::string testString = "try put string";
*output = [NSString stringWithUTF8String:testString.c_str()];
}
- (BOOL) _isQueueFull {
return self.queue.operationCount > MAX_OPERATIONS;
}
@end
如果我重复按下按钮,此更改会出现相同的错误。
眼前的问题与方块无关。您有一个代码片段:
- (IBAction)testCallMethod:(id)sender {
NSString *__autoreleasing * output;
[self.listOperationObj method1:output];
NSLog(@"Output: %@", *output);
}
那是行不通的,因为 output
不会指向有效的内存地址,当您尝试使用 *output = ...
取消引用未初始化的指针时,它会崩溃。
相反,
应该是:
- (IBAction)testCallMethod:(id)sender {
NSString *output;
[self.listOperationObj method1:&output];
NSLog(@"Output: %@", output);
}
现在 output
引用了一个真正的 NSString *
指针,您可以用对对象的引用来填充它。
还有第二个更深层次的问题,即对在操作中实例化的对象使用 * __autoreleasing *
引用。操作有自己的自动释放池,所以你有一个竞争条件,你在 testCallMethod
.
中使用它时释放了对象
相反,人们通常使用完成块将数据传回给调用者。因此:
- (IBAction)testCallMethod:(id)sender {
[self.listOperationObj method2:^(NSString *output) {
NSLog(@"Output: %@", output);
}];
}
和
- (void)method2:(void (^)(NSString *))completionHandler {
LOGFSTART
if([self _isQueueFull] == FALSE) {
WEAK
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
STRONG
[strongSelf _method2:completionHandler];
}];
[self.queue addOperation:operation];
// [operation waitUntilFinished]; // not needed any more
}
else {
LOGE(@"TokenMgr's queue is full, aborting operation");
}
LOGFEND
}
-(void)_method2:(void (^)(NSString *))completionHandler {
std::string testString = "try put string";
NSString *output = [NSString stringWithUTF8String:testString.c_str()];
completionHandler(output);
}
请注意,顺便说一句,这也解决了您的示例的另一个问题,即您必须在其中放置一个 waitUntilFinished
调用。你永远不应该从主线程调用 waitUntilFinished
。如果您像上面那样使用完成块,则不再需要。
我创建了一个实现了一些方法的 class。这些方法由另一个 class 调用,并通过 NSBlockOperation 进行管理。
我的 NSBlockOperation 工作正常,我在尝试计算变量时遇到问题:
EXC_BAD_ACCESS
我在互联网上做了很多研究,this 是最接近我的问题的。我试着像 sugerito 那样做,但你遇到了同样的问题。
你有什么建议吗?
编辑:
这是堆栈跟踪:
2015-05-09 15:24:45.976 OutParameters[12326:743087] Stack trace : (
0 OutParameters 0x000000010e5d6602 -[ListOperation _method1:] + 194
1 OutParameters 0x000000010e5d646f __25-[ListOperation method1:]_block_invoke + 95
2 Foundation 0x000000010e74257f __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__ + 7
3 Foundation 0x000000010e6830b2 -[NSBlockOperation main] + 98
4 Foundation 0x000000010e665774 -[__NSOperationInternal _start:] + 645
5 Foundation 0x000000010e665383 __NSOQSchedule_f + 184
6 libdispatch.dylib 0x00000001113f4614 _dispatch_client_callout + 8
7 libdispatch.dylib 0x00000001113db6a7 _dispatch_queue_drain + 2176
8 libdispatch.dylib 0x00000001113dacc0 _dispatch_queue_invoke + 235
9 libdispatch.dylib 0x00000001113de3b9 _dispatch_root_queue_drain + 1359
10 libdispatch.dylib 0x00000001113dfb17 _dispatch_worker_thread3 + 111
11 libsystem_pthread.dylib 0x0000000111761637 _pthread_wqthread + 729
12 libsystem_pthread.dylib 0x000000011175f40d start_wqthread + 13
)
修改后的代码:
- (IBAction)testCallMethod:(id)sender {
NSString * output;
[self.listOperationObj method1:&output];
NSLog(@"Output: %@", output);
}
和
@interface ListOperation : NSObject
-(void)method1:(NSString**)output;
@end
#define MAX_OPERATIONS 10
//define a log-level
static int logLevel = CSLOG_LEVEL_INFO;
@interface ListOperation ()
// Tail used to synchronize the methods
@property NSOperationQueue *queue;
@end
#pragma mark - Public methods
@implementation ListOperation
- (id)init {
self = [super init];
if(self) {
_queue = [NSOperationQueue new];
if(_queue) {
[_queue setMaxConcurrentOperationCount:1];
}else {
NSLog(@"TokenMgr creation failed: error creating operation queue");
self = nil;
}
}
return self;
}
-(void)method1:(NSString *__autoreleasing *)output{
LOGFSTART
if([self _isQueueFull] == FALSE) {
WEAK
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
STRONG
[strongSelf _method1:output];
}];
[self.queue addOperation:operation];
[operation waitUntilFinished];
}
else {
LOGE(@"TokenMgr's queue is full, aborting operation");
}
LOGFEND
}
#pragma mark - private methods
-(void)_method1:(NSString *__autoreleasing *)output{
std::string testString = "try put string";
*output = [NSString stringWithUTF8String:testString.c_str()];
}
- (BOOL) _isQueueFull {
return self.queue.operationCount > MAX_OPERATIONS;
}
@end
如果我重复按下按钮,此更改会出现相同的错误。
眼前的问题与方块无关。您有一个代码片段:
- (IBAction)testCallMethod:(id)sender {
NSString *__autoreleasing * output;
[self.listOperationObj method1:output];
NSLog(@"Output: %@", *output);
}
那是行不通的,因为 output
不会指向有效的内存地址,当您尝试使用 *output = ...
取消引用未初始化的指针时,它会崩溃。
相反, 应该是:
- (IBAction)testCallMethod:(id)sender {
NSString *output;
[self.listOperationObj method1:&output];
NSLog(@"Output: %@", output);
}
现在 output
引用了一个真正的 NSString *
指针,您可以用对对象的引用来填充它。
还有第二个更深层次的问题,即对在操作中实例化的对象使用 * __autoreleasing *
引用。操作有自己的自动释放池,所以你有一个竞争条件,你在 testCallMethod
.
相反,人们通常使用完成块将数据传回给调用者。因此:
- (IBAction)testCallMethod:(id)sender {
[self.listOperationObj method2:^(NSString *output) {
NSLog(@"Output: %@", output);
}];
}
和
- (void)method2:(void (^)(NSString *))completionHandler {
LOGFSTART
if([self _isQueueFull] == FALSE) {
WEAK
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
STRONG
[strongSelf _method2:completionHandler];
}];
[self.queue addOperation:operation];
// [operation waitUntilFinished]; // not needed any more
}
else {
LOGE(@"TokenMgr's queue is full, aborting operation");
}
LOGFEND
}
-(void)_method2:(void (^)(NSString *))completionHandler {
std::string testString = "try put string";
NSString *output = [NSString stringWithUTF8String:testString.c_str()];
completionHandler(output);
}
请注意,顺便说一句,这也解决了您的示例的另一个问题,即您必须在其中放置一个 waitUntilFinished
调用。你永远不应该从主线程调用 waitUntilFinished
。如果您像上面那样使用完成块,则不再需要。