setCompletionBlockWithSuccess not working
<p>I was trying to use the AFHTTPRequestOperation class to get data from an online php file, but I was having a bit of trouble.</p>

<pre><code>NSString *string = [NSString stringWithFormat:@"..."]; // i have a real url in place of the ...'s
NSURL *url = [NSURL URLWithString:string];
NSURLRequest *request = [NSURLRequest requestWithURL:url];

AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];
operation.responseSerializer = [AFXMLParserResponseSerializer serializer];
operation.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/html"];

[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    _data = [[operation responseData]dict];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Problem... problem.\n%@", error);
}];

[operation start];
</code></pre>

<p>I tried using this code, and it wouldn't create any errors, but whenever I put a breakpoint at the <code>_data = [[operation responseData]dict];</code> line, I would find it was empty.  Any help would be appreciated.  Thanks.</p>

<p>P.S.: This is not a duplicate, so please do not try to mark this question as a duplicate or vote this question down; I will lose a couple privileges.</p>