I have a question for you guys. I was wondering I generate another thread and set NSNotificationCenter to observe a event in the main thread?, what will be the best of doing this?
I'll really appreciate your help
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check this out. http://stackoverflow.com/questions/1973106/nsoperation-and-nsnotificationcenter-on-the-main-thread – madmik3 Aug 22 '13 at 02:45
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in this case they trying to take the notification to the main thread to update UI. In my case I need to observer something in the main thread from different thread. – Renata Aug 22 '13 at 02:52
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Notifications are delivered synchronously by the poster. There are no queues involved. When you call postNotification:, it will run all the observer code right then, sequentially for all observers, on the current thread, before returning.
If the observer wants to handle the observation on a different queue, then you should use dispatch_async or an NSOperation in the observer method to move the processing to the appropriate queue and then return.
Rob Napier
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in my case if use dispatch_async to create the observer can I observe and event on the main thread? – Renata Aug 22 '13 at 03:00
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Yes. Your notification callback will be called on whatever thread posts the notification. You can then use `dispatch_async` to move your processing over to whatever queue you would like. – Rob Napier Aug 22 '13 at 03:36
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You can handle notifications on a specific thread by using - (id)addObserverForName:(NSString *)name object:(id)obj queue:(NSOperationQueue *)queue usingBlock:(void (^)(NSNotification *))block.
As the documentation states, regarding the queue parameter:
The operation queue to which block should be added. If you pass nil, the block is run synchronously on the posting thread.
jrturton
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