iPhone:使用 NSURL 请求异步下载数据，而不是 [NSData datawithContents ofURL]

Question

嗨，我

是一个新手，我正在尝试从谷歌api网页下载地理编码数据。我用这个做了：代码：

        NSMutableString *urlStr = [[NSMutableString alloc] initWithString:temp];
        NSMutableString *address = [[NSMutableString alloc] initWithString:l.Address];
        [address appendString:@" "];
        [address appendString:l.CityName];
        [address appendString:@" "];
        [address appendString:l.State];
        [address appendString:@" "];
        [address appendString:l.PostalCode];
        NSArray *addressArray = [address componentsSeparatedByString:@" "];
        [address release];
        NSString *a = [addressArray componentsJoinedByString:@"+"];
        [urlStr appendString:a];
        [urlStr appendString:@"&sensor=false"];
        NSURL *url = [[NSURL alloc] initWithString:[urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
        NSData *data = [NSData dataWithContentsOfURL:url];

它

工作正常，但故障是它锁定了我的 GUI，因为它都是同步完成的。

有人建议我使用 NSURLrequest 异步执行此操作。所以我去了苹果网站。从那里我看到了他们的榜样。然而，我仍然卡住了。如何将上述同步请求代码转换为异步请求？到目前为止，这就是我所拥有的，但我不确定这是否有效......有点困惑...有人可以用这段代码指出我的方向吗？

        NSURL *url = [[NSURL alloc] initWithString:[urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
        //create NSURL request for asynchronous processing
        NSURLRequest *theRequest = [NSURLRequest requestWithURL:url
                                                  cachePolicy:NSURLRequestUseProtocolCachePolicy
                                              timeoutInterval:60.0];
        NSURLConnection *theConnection= [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
        if (theConnection) 
           {
            receivedData = [[NSMutableData data] retain];
           }
        else
           {
            // Inform the user that the connection failed.
           }

Answer 1

Using NSURLConnection

根据您构建代码的方式，您需要在成功完成时执行或通知其他对象（委托、通知）（连接DidFinishLoad：）或失败（连接：didFailWithError：）。