Petrifying Horror on Twitter: "@mjtsai I don't know of a circumstance where GCD would call you on some thread while that thread is already doing something."

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Petrifying Horror ‏@boredzo 22 Aug 2014

PSA: Don't start a second NSXMLParser on the same thread where another NSXMLParser is already running, or you will have a bad time.
3 retweets 5 likes
Michael Tsai ‏@mjtsai 22 Aug 2014

@boredzo So all bets are off if you're using GCD and don't know the actual thread? Is NSXMLDocument safe?
Petrifying Horror ‏@boredzo 22 Aug 2014

@mjtsai You can use a serial queue, but not concurrent, for that reason. NSXMLDoc/Element: Probably the same story; haven't looked deeply.
Petrifying Horror ‏@boredzo 22 Aug 2014

@mjtsai Actually, concurrent may be fine. Not like GCD is going to call you twice at the same time on the same thread.
Michael Tsai ‏@mjtsai 22 Aug 2014

@boredzo You can't ensure that they won't be interleaved on the same thread. But it's OK, I guess, since not called from a callback.

‏@boredzo

@mjtsai I don't know of a circumstance where GCD would call you on some thread while that thread is already doing something.

7:14 PM - 22 Aug 2014

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