如何发送异步URL请求？

Question

我想知道如何获得仅返回值1或0 ....异步URL请求。

目前我做了这种方式：

 NSString *UTCString = [NSString stringWithFormat:@"http://web.blah.net/question/CheckQuestions?utc=%0.f",[lastUTCDate timeIntervalSince1970]]; 
     NSLog(@"UTC String %@",UTCString); 
     NSURL *updateDataURL = [NSURL URLWithString:UTCString]; 
     NSString *checkValue = [NSString stringWithContentsOfURL:updateDataURL encoding:NSASCIIStringEncoding error:Nil]; 
     NSLog(@"check Value %@",checkValue); 

这个作品，但它是挡住了我的主线程，直到我得到的答复从URL回来了，我该如何设置它，所以它会做它另一个线程而不是主线程？

编辑：ANSWER 我结束我的upcalling功能与此，它工作得很好:)

[self performSelectorInBackground:@selector(shouldCheckForUpdate) withObject:nil]; 

Answer 1

可以使用NSURLConnection类

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]]; 
[[[NSURLConnection alloc] initWithRequest:request delegate:self] autorelease]; 

，并处理其响应，并使用其委托的方法错误。

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data 
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 
- (void)connectionDidFinishLoading:(NSURLConnection *)connection 

你可以找到实现NSURLConnection的

的

• Apple docs: Using NSURLConnection
• How To Use iOS NSURLConnection By Example

编辑：虽然NSURLConnection是由苹果提供的是把URL请求的更多推荐的方式。但是，我发现AFNetworking库非常省时，易于实现，并且强大而简单，因为它是第三方实现的。你应该试试看。

Answer 2

使用NSURLConnection，让你的要求。 然后您就可以开始与NSURLConnection的的方法同步或异步连接：

加载数据同步方式

+ sendSynchronousRequest:returningResponse:error: 

加载数据不同步

+ connectionWithRequest:delegate: 
– initWithRequest:delegate: 
– initWithRequest:delegate:startImmediately: 
– start 

检查苹果开发者API参考的NSURLConnection类。

Answer 3

试试这个：

.H：

NSMutableData *responseData; 

.M：

- (void)load 
{ 
    NSURL *myURL = [NSURL URLWithString:@"http://www.example.com"]; 
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:myURL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60]; 

    [[NSURLConnection alloc] initWithRequest:request delegate:self]; 
} 

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 
{ 
    responseData = [[NSMutableData alloc] init]; 
} 

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data 
{ 
    [responseData appendData:data]; 
} 

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 
{ 
    [responseData release]; 
    [connection release]; 
    [textView setString:@"Unable to fetch data"]; 
} 

- (void)connectionDidFinishLoading:(NSURLConnection *)connection 
{ 
    NSLog(@"Succeeded! Received %d bytes of data",[responseData 
                length]); 
    NSString *txt = [[[NSString alloc] initWithData:responseData encoding: NSASCIIStringEncoding] autorelease]; 
} 

Answer 4

有一个在iOS版的XCode文档称为LazyTableImages一个例子。在滚动停止后，这会在屏幕上显示一个异步URL以及异步图像加载到UITableView单元格。协议的优秀示例，异步数据处理等。

Answer 5

无耻地从https://gist.github.com/knmshk/3027474复制。所有积分均为https://gist.github.com/knmshk。

xmlData = [[NSMutableData alloc] init]; 
NSURL *url = [NSURL URLWithString: 
@"http://forrums.bignerdranch.com/smartfeed.php?" 
@"limit=NO_LIMIT&count_limit20&sort_by=standard&" 
@"feed_type=RSS2.0&feed_style=COMPACT"]; 
NSURLRequest *request = [NSURLRequest requestWithURL:url]; 
//connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES]; 
NSOperationQueue *queue = [[NSOperationQueue alloc]init]; 
[NSURLConnection sendAsynchronousRequest:request 
            queue:queue 
         completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){ 
          if (error) { 
           xmlData = nil; 
           NSLog(@"error:%@", error.localizedDescription); 
          } 
          [xmlData appendData:data]; 
         }];