iOS Finish task before app did enter background

[donaghy]

Hi all. My application attempts to connect to a webservice and sending, receiving and parsing this information can be time consuming. This isn't a problem until the application is about to enter the background. The given 5 seconds to complete tasks isn't enough time so i would like to run it in the background until its finished. It would not take more than 60 seconds to complete. Does anyone know how i could do this? The task is running on the main thread so could I beginBackgroundTaskWithExpirationHandler and wait until the main thread is finished executing? Though I would assume the process of entering the background is on the main thread and i would have an infinite loop. Help appreciated.

 

[firewood]

You need to run the long network task in a background thread or async to begin with. Or else it will block the UI run loop and thus block the resign/suspend delegates and the OS will kill the app instead.

 

[donaghy]

I have put the URLConnection work in an operation queue, when the application is about to move in the background i check if the operation is still running and wait until it finishes.

dispatch_async(dispatch_get_global_queue(0, 0), ^{ 
		NSLog(@"Starting background task with %f seconds remaining", app.backgroundTimeRemaining);
		
		while ([o isExecuting]) 
		{
		}
		
		NSLog(@"Finishing background task with %f seconds remaining", app.backgroundTimeRemaining);
		[app endBackgroundTask:taskId];
	});

However in the connection code i get an error at this line:

[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:1]];

I'm not quite sure why it would fall at this line. Does the operation not run in it's own thread and current run loop is for the given thread?

 

[donaghy]

I've read that NSRunloop is not thread safe and should not be run off the main thread. This being the case is there any alternative i can use? The code is quite simple:

while(running) 
	{
		if ([NSRunLoop currentRunLoop]) 
		{
			[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:1]];
		}
	}

I just need to wait for 1 second before checking if the URL connection is still running each time.