dispatch_queue_t still blocking main thread

Question

I want to fire off a method and have it run in the background - I do not care what really happens to it after it is started.

So in my main viewDidLoadMethod I have all o

Answer 1

To my understanding, ASIHTTPRequest startSynchronous requires NSRunLoop, and GCD serial queue thread doesn't have NSRunLoop. Thus, it doesn't work.

And your code seems that GCD serial queue is not needed at all. I think GCD global queue works fine with your code. For example,

- (void)getNewImages
{
    dispatch_queue_t queue =
        dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0);

    /* snip */
    for (Manufacturer *m in self.manufacturers)
    {
        /* snip */
        ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
        [request setCompletionBlock:^{
            /* snip */
            dispatch_async(queue, ^{
                [responseString writeToFile:fileName atomically:YES encoding:NSUTF8StringEncoding error:nil];
            });

            for (NSDictionary* dict in array) {
                /* snip */
                ASIHTTPRequest *imageRequest = [ASIHTTPRequest requestWithURL:url];
                [imageRequest setCompletionBlock:^{
                    /* snip */
                    dispatch_async(queue, ^{
                        [responseData writeToFile:[savePath stringByReplacingOccurrencesOfString:@"%20" withString:@" "] atomically:YES];
                    });
                }];
                /* snip */
                [imageRequest startAsynchronous];
            }
            /* snip */
        }];
        /* snip */
        [request startAsynchronous];
    }
}

getNewImages method should be executed on the main thread, it requires the NSRunLoop of the main thread.