grand central dispatch - IOS dispatch_async view will disappear -

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i using dispatch_async , block retrieve server data every 3 seconds or so. method of handling view either disappearing or user shutting program down?

would boolean flag async block checks every , then? if so, if view exits while async block sleeping?

you cannot cancel dispatch call, best bet move nsoperation instead. there highly relevent video wwdc 2012, session 211 - building concurrent user interfaces on ios covers precisely kind of problem describe. suggest watch it.

the basic approach create nsblockoperation can check -iscancelled property on return if gets cancelled. can cancel operation in viewdiddisappear.

an alternative approach use nstimer can invalidated/cancelled. might simplest solution given description of code doing.


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