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Sync-Async Pair Pattern – Easy concurrency on iOS

Apple provides many tools for implementing concurrency in your application. NSOperationQueue, GCD, or simply using performSelectorInBackground:withObject: that is available on each and every object, are just some examples. The tools are there, yet implementing good concurrency is hard.

The solution I have found is not yet another tool, or framework, but a simple pattern. I have not found an existing name for the pattern so I call it Sync-Async Pair. The idea is to hide the complexity of asynchronous calls and call-back behind a facade, and have a straightforward synchronous implementation. An implementation that is easy to write, test and extend.

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