在AFNetworking 请求数据失败的block里面 复制一下代码 就可以看到服务器返回的错误提示信息

NSData * data = error.userInfo[@"com.alamofire.serialization.response.error.data"];
        NSString * str = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        NSData *data1 = [str dataUsingEncoding:NSUTF8StringEncoding];
        NSDictionary *errorDic = [NSJSONSerialization JSONObjectWithData:data1 options:0 error:nil];

        NSLog(@"服务器的错误原因:%@",errorDic);

        [SVProgressHUD showInfoWithStatus:errorDic[@"error"][@"message"]];