ios - AF网络 2 : canceling batch requests

Question

我正在使用 AFNetworking2 代码来处理请求。我从示例代码中复制并粘贴，并将上传操作更改为下载。我需要取消 Controller 消失的下载操作。我正在尝试实现取消:

    [[self.imagesQueue.operations 
filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) 
{ return [evaluatedObject isKindOfClass:[AFHTTPRequestOperation class]]; }]] makeObjectsPerformSelector:@selector(cancel)];

批量请求(下载图片):

-(void) startDownloadImages {

    NSMutableArray *mutableOperations = [NSMutableArray array];
    //self.downloadOperations = [NSMutableArray array];
    for (NSString *str in _project.frames) {

        NSURLRequest *request =
        [[AFHTTPRequestSerializer serializer] requestWithMethod:@"GET"
                                                      URLString:str
                                                     parameters:nil];

        AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
        [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {

         NSLog(@"OK %@", str);


        } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
            NSLog(@"FAILS %@", str);
        }];

        [mutableOperations addObject:operation];
    }

    NSArray *operations =
    [AFURLConnectionOperation batchOfRequestOperations:mutableOperations
                                         progressBlock:^(NSUInteger numberOfFinishedOperations, NSUInteger totalNumberOfOperations) {
        NSLog(@"%lu of %lu complete", (unsigned long)numberOfFinishedOperations, (unsigned long)totalNumberOfOperations);
    } completionBlock:^(NSArray *operations) {
        NSLog(@"All operations in batch complete");

    }];

    self.imagesQueue = [[NSOperationQueue alloc] init];
    self.imagesQueue.name = @"com.imagesqueue";
    self.imagesQueue.maxConcurrentOperationCount = 1;

    [self.imagesQueue addOperations:operations waitUntilFinished:NO];
    //[[NSOperationQueue mainQueue] addOperations:operations waitUntilFinished:NO];
}

一系列启动和取消导致 EXC_BREAKPOINT(代码=EXC_ARM_BREAKPOINT，子代码=0xdefe):

libdispatch.dylib`dispatch_group_leave:
    0x37e1e7d8:  dmb    ishst
    0x37e1e7dc:  ldrex  r1, [r0, #40]
    0x37e1e7e0:  adds   r1, #1
    0x37e1e7e2:  strex  r2, r1, [r0, #40]
    0x37e1e7e6:  cmp    r2, #0
    0x37e1e7e8:  bne    0x37e1e7dc                ; dispatch_group_leave + 4
    0x37e1e7ea:  cmp.w  r1, #4294967295
    0x37e1e7ee:  ble    0x37e1e7fe                ; dispatch_group_leave + 38
    0x37e1e7f0:  mvn    r2, #2147483648
    0x37e1e7f4:  cmp    r1, r2
    0x37e1e7f6:  it     eq
    0x37e1e7f8:  beq.w  0x37e21df8                ; _dispatch_group_wake
    0x37e1e7fc:  bx     lr
    0x37e1e7fe:  trap   
    0x37e1e800:  nop    
    0x37e1e802:  nop 

有什么建议吗？

Answer 1

尝试将 str 声明为 block 变量(您正在 block 中访问它):

__block NSString *str;

for (str in _project.frames) {

你也可以尝试在执行取消选择器之前检查操作是否已经完成。

在 View 将消失的方法中，您可以调用图像队列上的 cancelAllOperations 来取消所有剩余的操作。