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NSString *baseURLStr = @"http://myserverurl/";
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL
                                                      URLWithString:[baseURLStr stringByAppendingFormat:@"%d/%d.json", int1, int2]]];
NSData *data = [NSURLConnection sendSynchronousRequest:request
                                     returningResponse:nil error:nil];
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];  

NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
    if (!data) {
        NSLog(@"%s: sendAynchronousRequest error: %@", __FUNCTION__, connectionError);
        return;
    } else if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
        NSInteger statusCode = [(NSHTTPURLResponse *)response statusCode];
        if (statusCode != 200) {
            NSLog(@"%s: sendAsynchronousRequest status code != 200: response = %@", __FUNCTION__, response);
            return;
        }
    }

    NSError *parseError = nil;
    NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
    if (!dictionary) {
        NSLog(@"%s: JSONObjectWithData error: %@; data = %@", __FUNCTION__, parseError, [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
        return
    }

    // now you can use your `dictionary` object
}];

// Note, with asynchronous connection, do not try to use `data` 
// or the object you parsed from theJSON after the block, here.
// Use it above, inside the block.