ios开发 - 获取从http上下载文件的大小

1. - (void)connectionNSURLConnection *)connection didReceiveResponseNSURLResponse *)response{
   
2.     NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
   
3.     if(httpResponse && [httpResponse respondsToSelectorselector(allHeaderFields)]){
   
4.         NSDictionary *httpResponseHeaderFields = [httpResponse allHeaderFields];
   
5.         
   
6.         total_ = [[httpResponseHeaderFields objectForKey"Content-Length"] longLongValue];
   
7.         
   
8.         //NSLog(@"%lld", total_);
   
9.     }
   
10. }