Question

I create an object on a seperate thread using NSThread.

NSThread* myThread = [[[NSThread alloc] initWithTarget:self selector:@selector(createNewObject:) object:elements] autorelease];
[myThread start];  // Actually start the thread

That Object waits for an event. When that event occurs a notification is posted on the default notification center.

My AppController observes that notification and runs a selector.

NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
        [nc addObserver:self selector:@selector(myMethod:) name:MyNotification object:nil];

Question: Does the method (myMethod:) from the selector run on the main thread or on the thread from above (myThread) ?

Answer 1

Same thread in which you post the notification.

In a multithreaded application, notifications are always delivered in the thread in which the notification was posted, which may not be the same thread in which an observer registered itself. (Source)

Footnote: Objects can’t wait for events. Objects just exist. Methods can wait for events.