On 22 Feb 2013, at 8:56 AM, Dave <d...@looktowindward.com> wrote:
> A (Background) thread has two choices at this stage:
>
> 1. Call aSyncComputePIToAZillionPlacesWithDelegate and provide a delegate
> that will be called back with the result.
>
> 2. Call syncComputePIToAZillionPlaces get the result inline.
>
> As long as the Background Thread doesn't have more work to do in parallel
> with the Compute PI operation, why is option 2 better than option 1.
>
> I think that option 1 is by far the best solution and I can't understand why
> anyone would choose option 2!!
You misconceive what Apple and the other replies are telling you. The whole
point of the async API is that _you don't create a background thread at all._
You call the method that starts the async process on the main thread, the
implementing class does all the background processing as/if needed (and does it
correctly), and it reports progress, errors, and completions on the main thread.
You get:
* No threading issues (Apple has already done them correctly)
* A service that can make an optimal choice between a background thread and a
runloop source
* The ability to cancel (no threading issues)
* Progress events (no threading issues)
* The ability to detect security issues on-the-fly (no threading issues)
* Authentication (no threading issues)
* Error handling (no threading issues)
* The ability to interface with your controllers and views in a way that is
factored out of the asynchronous process into your main-thread delegate methods
(no threading issues)
You get none of this if you toss a synchronous call into a dispatch_async() and
call it a day.
That's only what I can think of for NSURLConnection; your example of a
calculation of pi is simplified to the point of being a straw man, and better
handled with an NSOperation.
— F
--
Fritz Anderson
Xcode 4 Unleashed: 4.5 supplement for free!
http://www.informit.com/store/xcode-4-unleashed-9780672333279
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