NSThread exit when app terminate

Question

I have an iphone app, it run some thread to compute search. The search is made calling a time consuming function from a library.

I need to exit from the thread when the app is terminating, otherwise the thread continue to run and the search create problem when i reopen the app.

I tried to subscribe in the thread

 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(mainApplicationWillTerminate) name:@"UIApplicationWillTerminateNotification" object:nil];

And in mainApplicationWillTerminate

-(void)mainApplicationWillTerminate;
{
    [NSThread exit];
}

The problem is still present, any idea?

Answer 1

As stated in the docs you should avoid using [NSThread exit]. In general, to avoid memory leaks and other disasters, a thread should never be stopped "from the outside". A thread should always exits by itself.

In your thread main loop you should check if the thread was cancelled:

if ([[NSthread currentThread] isCancelled]) {
    return;
}

To cancel it you call its "cancel" method from another thread.

In your case you should setup an application delegate (see UIApplicationDelegate)

- (void)applicationWillTerminate:(UIApplication *)application
{
    [myThread cancel];
}

Better have a look to the nice NSOperation class also.