iOS 从网页下载数据的问题，NSURL

Question

需要您的快速建议。我正在创建一个“货币转换器”iPhone 应用程序来从谷歌货币网站检索数据。下载 USD 字符串完美运行 ->澳元、美元->加元、美元->港元、美元->匈牙利福林、美元->日元。但是，我不明白为什么在尝试检索 USD->KRW 和 USD->ZMK 时不工作并返回NULL。请参考下面的代码。

 -(void)loadData:(NSString*)countryName{
    self.responseData = [NSMutableData data];
        NSString *responseURL = [NSString stringWithFormat: @"http://www.google.com/ig/calculator?q=1USD=?%@", countryName];
        NSLog(@"URL:%@", responseURL);

        NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:responseURL]];

        theConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

 }

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

         NSString* responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
         NSLog(@"This is the responseString %@", responseString);
             [responseString release];


 }
 - (void)viewDidLoad {
         [super viewDidLoad];
         [self loadData:@"AUD"];
         [self loadData:@"CAD"];
         [self loadData:@"HKD"];
         [self loadData:@"HUF"];
         [self loadData:@"JPY"];
         [self loadData:@"KRW"];
         [self loadData:@"ZMK"];
  }

控制台结果：

 2011-09-30 18:03:50.877 Converter[1691:f503] URL:http://www.google.com/ig/calculator?q=1USD=?AUD
 2011-09-30 18:03:50.879 Converter[1691:f503] URL:http://www.google.com/ig/calculator?q=1USD=?CAD
 2011-09-30 18:03:50.879 Converter[1691:f503] URL:http://www.google.com/ig/calculator?q=1USD=?HKD
 2011-09-30 18:03:50.879 Converter[1691:f503] URL:http://www.google.com/ig/calculator?q=1USD=?HUF
 2011-09-30 18:03:50.879 Converter[1691:f503] URL:http://www.google.com/ig/calculator?q=1USD=?JPY
 2011-09-30 18:03:50.879 Converter[1691:f503] URL:http://www.google.com/ig/calculator?q=1USD=?KRW
 2011-09-30 18:03:50.879 Converter[1691:f503] URL:http://www.google.com/ig/calculator?q=1USD=?ZMK
 2011-09-30 18:03:50.952 Converter[1691:f503] This is the responseString {lhs: "1 U.S. dollar",rhs: "1.02228583 Australian dollars",error: "",icc: true}
 2011-09-30 18:03:50.962 Converter[1691:f503] This is the responseString {lhs: "1 U.S. dollar",rhs: "7.79149947 Hong Kong dollars",error: "",icc: true}
 2011-09-30 18:03:50.966 Converter[1691:f503] This is the responseString {lhs: "1 U.S. dollar",rhs: "215.889465 Hungarian forints",error: "",icc: true}
 2011-09-30 18:03:50.982 Converter[1691:f503] This is the responseString {lhs: "1 U.S. dollar",rhs: "1.03910031 Canadian dollars",error: "",icc: true}
 2011-09-30 18:03:50.993 Converter[1691:f503] This is the responseString {lhs: "1 U.S. dollar",rhs: "76.5579544 Japanese yen",error: "",icc: true}
 2011-09-30 18:03:51.010 Converter[1691:f503] This is the responseString (null)
 2011-09-30 18:03:51.047 Converter[1691:f503] This is the responseString (null)

请帮忙，非常感谢。

Answer 1

您不应该与所有请求共享 responseData，因为它们是异步发送的，它们都会在随机时间完成，并且您可能将所有收到的数据（来自所有请求）写入 响应数据。每个请求都应该有自己的资源（resourceData、theConnection）。

查看 ASIHTTPRequest 以获得简单的解决方案。