Question

I am working on performing some tasks in the background every 60 seconds. The background task is the server requests documents to be downloaded form the website. The main thread/UI seems to be locking when the request is done and I am saving the data to sqlite.

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
        [NSThread detachNewThreadSelector:@selector(startTheBackgroundSync) toTarget:self withObject:nil];
        [pool release]; 

- (void)startTheBackgroundSync {  

    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];  

  //  [self performSelectorInBackground:@selector(moveSynctoBack) withObject:nil];  
  //  [self performSelectorOnMainThread:@selector(makeMyProgressBarMoving) withObject:nil waitUntilDone:NO];  

    serverSync = [[[ServerSync alloc]init]autorelease];
    while (1==1) {
        serverSync.delegate = self;
        [serverSync syncNow:nil];
        [NSThread sleepForTimeInterval:120];
    }
    [pool release];  
    [serverSync release];

}  

While the looping does not lock up the main thread, but when ASIHTtpRequest finished with the data it locks up the ui for a second.

Answer 1

The finished selector of an ASIHTTPRequest will always be performed on the main thread. Therefore you shouldn’t do long running tasks there.

Instead of launching a new thread you can schedule a repeated NSTimer:

NSTimer* timer = [NSTimer scheduledTimerWithTimeInterval:120 target:self selector:@selector(backgroundSync) userInfo:nil repeats:YES];

… with the following action method:

-(void) backgroundSync
{
  ServerSync* serverSync = [[[ServerSync alloc]init]autorelease];
  serverSync.delegate = self;
  [serverSync syncNow:nil];
}

Be sure that you use the startAsynchronous-method in ServerSync to start the request!

Furthermore I’d recommend to implement a singleton and then use it like that:

-(void)init {
   [[ServerSync sharedSync] setDelegate:self];
}

-(void) backgroundSync
{
   [[ServerSync sharedSync] syncNow];
}