JSON解析器解析失败判断

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    [connection release];

    NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
    [responseData release];

    NSError *error;
    SBJSON *json = [[SBJSON new] autorelease];
    NSArray *luckyNumbers = [json objectWithString:responseString error:&error];
    [responseString release];   

    if (luckyNumbers == nil)
        label.text = [NSString stringWithFormat:@"JSON parsing failed: %@", [error localizedDescription]];
    else {
        NSMutableString *text = [NSMutableString stringWithString:@"Lucky numbers:\n"];

        for (int i = 0; i <; [luckyNumbers count]; i++)
            [text appendFormat:@"%@\n", [luckyNumbers objectAtIndex:i]];

        label.text =  text;
    }
}