相关疑难解决方法(0)

我有自己的方法,以块作为参数.我想跟踪NSDictionary中的那个块.将块添加到字典的最佳方法是什么？

我尝试了这段代码但是在执行下面的行(setObject ...)后,字典仍然是空的.我认为这是因为该块不是NSObject类型.但是这样做的正确方法是什么？

- (void)startSomething:(NSURLRequest*)request block:(void (^)(NSURLResponse*, NSData*, NSError*))handler {

    NSURLConnection *connection = [NSURLConnection connectionWithRequest:request delegate:self];

    [pendingRequests setObject:handler forKey:connection];
}

编辑:

没关系.我不知道我在想什么.3分:

1. 块是objc对象
2. 错字:setObject应该是setValue
3. forKey是一个字符串,因此它应该是[连接描述]或类似的东西

无论如何我现在解决了我的问题:

- (void)startSomething:(NSURLRequest*)request block:(void (^)(NSURLResponse*, NSData*, NSError*))handler {

    NSURLConnection *connection = [NSURLConnection connectionWithRequest:request delegate:self];
    [pendingRequests setValue:handler forKey:[connection description]];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {

        void (^handler)(NSURLResponse*, NSData*, NSError*);
        handler = [pendingRequests valueForKey:[connection description]];
        handler(nil, nil, nil);
    });
}

为了更好地理解块的行为,我一直试图理解这次崩溃背后的原因.我有一个非常简单的类来触发这个崩溃.

@implementation BlockCrashTest

- (void)doSomething
{
    dispatch_queue_t queue = dispatch_queue_create("com.queue.test", DISPATCH_QUEUE_SERIAL);

    __weak typeof(self) weakSelf = self;

    dispatch_block_t block = ^{

        __strong typeof(weakSelf) strongSelf = weakSelf;

        dispatch_group_t group = dispatch_group_create();

        dispatch_time_t time = dispatch_time(DISPATCH_TIME_NOW, 2 * NSEC_PER_SEC);

        dispatch_group_enter(group);
        [strongSelf performSomethingAsync:^{
            dispatch_group_leave(group);
        }];

        if(dispatch_group_wait(group, time) != 0) {
            NSLog(@"group already finished");
        }
    };
    dispatch_async(queue, block);
}

- (void)performSomethingAsync:(void(^)(void))completion
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        sleep(5);
        completion();
    });
}

- (void)dealloc
{
    NSLog(@"released object");
}

@end

现在,如果我分配类并简单地调用方法doSomething,

BlockCrashTest *someObject = [[BlockCrashTest alloc] init]; …