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dispatch_once
dispatch_once. Executes a block object only once for the lifetime of an application. Availability. iOS 4.0+; iPadOS 4.0+; macOS 10.6+; Mac Catalyst 13.1+ ...
Jan 13, 2013dispatch_once is one of those tools, and has applicability outside of making shared class instances. It's very low overhead, with ...
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Apr 11, 2016我们的应用程序调用的入口 void dispatch_once(dispatch_once_t *val, dispatch_block_t block) { struct Block_basic *bb = (void *)block; // 2.
Jun 6, 2014The unique requirements of dispatch_once allow it to work around the problem in an unconventional way. By waiting a sufficiently long time ...
How dispatch_once works ... No matter how many times you invoke sharedDowloader . The returned instance is the same. ... In dispatch_once_f function, if the block ...
dispatch_once - Man Page. execute a block only once. Synopsis. #include <dispatch/dispatch.h>. void dispatch_once ( dispatch_once_t *predicate , void ...
And here's the quote from dispatch_once documentation: The predicate must point to a variable stored in global or static scope. The result of using a predicate ...
Initializing on the main thread using dispatch_once. April 2, 2014. We recently refactored the Khan Academy iOS app to use Core Data instead of the ...

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