Databases
StackOverflow2013
Postsdbo
POAsynchronous request to the server from background thread
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POAsynchronous request to the server from background thread
    primarykey
    data
    text
    <p>I've got the problem when I tried to do asynchronous requests to server from background thread. I've never got results of those requests. Simple example which shows the problem:</p> <pre><code>@protocol AsyncImgRequestDelegate -(void) imageDownloadDidFinish:(UIImage*) img; @end @interface AsyncImgRequest : NSObject { NSMutableData* receivedData; id&lt;AsyncImgRequestDelegate&gt; delegate; } @property (nonatomic,retain) id&lt;AsyncImgRequestDelegate&gt; delegate; -(void) downloadImage:(NSString*) url ; @end @implementation AsyncImgRequest -(void) downloadImage:(NSString*) url { NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:20.0]; NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; if (theConnection) { receivedData=[[NSMutableData data] retain]; } else { } } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { [delegate imageDownloadDidFinish:[UIImage imageWithData:receivedData]]; [connection release]; [receivedData release]; } @end </code></pre> <p>Then I call this from main thread </p> <pre><code>asyncImgRequest = [[AsyncImgRequest alloc] init]; asyncImgRequest.delegate = self; [self performSelectorInBackground:@selector(downloadImage) withObject:nil]; </code></pre> <p>method downloadImage is listed below:</p> <pre><code>-(void) downloadImage { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; [asyncImgRequest downloadImage:@"http://photography.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Photography/Images/POD/l/leopard-namibia-sw.jpg"]; [pool release]; } </code></pre> <p>The problem is that method imageDownloadDidFinish is never called. Moreover none of methods </p> <pre><code>- (void)connectionDidFinishLoading:(NSURLConnection *)connection - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse*)response </code></pre> <p>are called. However if I replace</p> <pre><code> [self performSelectorInBackground:@selector(downloadImage) withObject:nil]; </code></pre> <p>by </p> <pre><code> [self performSelector:@selector(downloadImage) withObject:nil]; </code></pre> <p>everything is working correct. I assume that the background thread dies before async request is finished it job and this causes the problem but I'm not sure. Am I right with this assumptions? Is there any way to avoid this problem?</p> <p>I know I can use sync request to avoid this problem but it's just simple example, real situation is more complex. </p> <p>Thanks in advance. </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USMicah Hainline
    1. USDmytro
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    3. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POAsynchronous request to the server from background thread
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POAsynchronous request to the server from background thread
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POAsynchronous request to the server from background thread
      1. USSujee Maniyam
      1. VTFavorite
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload