Looking at the docs, dispatch_once takes care of the synchronization for you:
https://developer.apple.com/library/mac/ipad/#documentation/Performance/Reference/GCD_libdispatch_Ref/Reference/reference.html It should therefore be thread safe to use without any additional synchronization code. Sent from my New iPad. I blame all typos on the Fruit Company. May have been dictated. On 2012-11-12, at 7:56 AM, "Gerriet M. Denkmann" <gerr...@mdenkmann.de> wrote: > I have a property: > > @property (readonly) NSDictionary *someDictionary; > > This property should be computed on demand, and should be accessible by > several threads. > > My current implementation is: > > - (NSDictionary *)someDictionary; > { > static NSDictionary *someDictionary; > static dispatch_once_t justOnce; > dispatch_once( &justOnce, ^ > { > // create a temp dictionary (might take some time) > someDictionary = temp; > } > ); > > return someDictionary; > } > > The first thread which needs someDictionary will trigger its creation. Ok. > > But what happens when another thread wants to access someDictionary while it > is still being created? I guess it will receive just nil. > This would be not correct; it really should wait until the dictionary is > ready. > > How to achieve this? Use a lock? Use @synchronize? > > 10.8.2 with Arc. > > > Gerriet. > > > _______________________________________________ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/cocoa-dev/mtabini%40me.com > > This email sent to mtab...@me.com _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
