Objective-C-sendAsynchronousRequest什么都不做？

Question

I have this code:

NSURLRequest *urlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://example.com/"]];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];

[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
    NSLog(@"handler block executed!\n");            
}];

The problem is that the handler blocks is not working. It never executes.

I have read on Xcode docs this:

A completion handler block that runs whenever the transfer finishes or fails.

So, why whenever I execute this code, the handler block doesn't run? It should run even if the call fails, shouldn't it?

Answer 1

OK, I found the solution thanks to Kevin. The problem was exactly that ARC was deallocating the NSOperationQueue before the handler block call. I found the snippet on this japanese blog .

#import <Foundation/Foundation.h>
#import <dispatch/dispatch.h>

int main(int argc, char *argv[])
{
    @autoreleasepool {
        NSOperationQueue *queue = [[NSOperationQueue alloc] init];
        NSURL *url = [NSURL URLWithString:@"http://www.google.com/"];
        NSURLRequest *request = [NSURLRequest requestWithURL:url];

        dispatch_semaphore_t s = dispatch_semaphore_create(0);

        [NSURLConnection sendAsynchronousRequest:request
            queue:queue
            completionHandler:^(NSURLResponse *r, NSData *d, NSError *e) {
            NSLog(@"%@", r);
            dispatch_semaphore_signal(s);
        }];

        dispatch_semaphore_wait(s, DISPATCH_TIME_FOREVER);
        dispatch_release(s); // <= remove this if you are using ARC.
    }
    return 0;
}