如何發送異步URL請求？

Question

我想知道如何獲得僅返回值1或0 ....異步URL請求。

目前我做了這種方式：

 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); 

這個作品，但它是擋住了我的主線程，直到我得到的答覆從URL回來了，我該如何設置它，所以它會做它另一個線程而不是主線程？

編輯：ANSWER 我結束我的upcalling功能與此，它工作得很好:)

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

Answer 1

可以使用NSURLConnection類

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

，並處理其響應，並使用其委託的方法錯誤。

- (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 

你可以找到實現NSURLConnection的

的

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

編輯：雖然NSURLConnection是由蘋果提供的是把URL請求的更多推薦的方式。但是，我發現AFNetworking庫非常省時，易於實現，並且強大而簡單，因爲它是第三方實現的。你應該試試看。

Answer 2

使用NSURLConnection，讓你的要求。 然後您就可以開始與NSURLConnection的的方法同步或異步連接：

加載數據同步方式

+ sendSynchronousRequest:returningResponse:error: 

加載數據不同步

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

檢查蘋果開發者API參考的NSURLConnection類。

Answer 3

試試這個：

.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

有一個在iOS版的XCode文檔稱爲LazyTableImages一個例子。在滾動停止後，這會在屏幕上顯示一個異步URL以及異步圖像加載到UITableView單元格。協議的優秀示例，異步數據處理等。

Answer 5

無恥地從https://gist.github.com/knmshk/3027474複製。所有積分均爲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]; 
         }];