Re: Integrating NSOutputStream and NSOperation
Re: Integrating NSOutputStream and NSOperation
- Subject: Re: Integrating NSOutputStream and NSOperation
- From: Motti Shneor <email@hidden>
- Date: Fri, 13 Nov 2015 16:38:52 +0200
| Hello Jens, and thanks for the very useful information.
I still don't quite understand how to employ CFWriteStreamSetDispatchQueue. Can an NSOperation somehow obtain the dispatch_queue on which it is running?
I know NSOperationQueue has an accessor for its underlying dispatch_queue, but actual NSOperations are spawned in arbitrary threads - so I'm not sure about their dispatch_queue (if they run on a dispatch_queue at all).
Supposedly I'd schedule my output stream on the OperationQueue's dispatch_queue. What kind of synchronization can I expect? Does this promise that stream events won't happen concurrently as my NSOperation's main()?
Also - If I need to reschedule the stream to each operation's dispatch_queue (provided they can each have a different one) is it advisable to reschedule a stream mid-running? how costly this is? Can I lose events that way?
However - my original hesitation remains - On 11 בנוב 2015, at 18:53, Jens Alfke wrote: On Nov 11, 2015, at 3:46 AM, Motti Shneor < email@hidden> wrote:
If I (upon starting my operation) schedule the outputStream on the current operation’s runloop like thus:
[self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
That won’t work because dispatch queues (other than main) and NSOperationQueues don’t have runloops. (If you call +currentRunLoop you do create a new runloop for whatever thread the queue is using, but that runloop won’t do anything because there’s no outer loop on that thread servicing it.) If I can change the outputStream’s scheduling to use the same of my currently running operation - that should solve my synchronizing problem. My operation can bail safely, and be re-called on its own thread, without concurrency.
You can use CFWriteStreamSetDispatchQueue to schedule the stream on a queue instead of a runloop.
—Jens
Motti Shneor, CEO, suMac LTD. Software Development for the Macintosh
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