That’s not what the documentation says:
> If YES, the current thread is blocked until all of the specified operations
> finish executing. If NO, the operations are added to the queue and control
> returns immediately to the caller.
So, if you’re experiencing different behavior, I would say that’s a bug that
should be filed.
That doesn’t solve your question, though. Have you tried using dispatch
semaphores? They’re a pretty easy way to synchronize tasks:
> dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
>
> [self performLongRunningAsynchronousTaskWithCompletionHandler:^{
> dispatch_semaphore_signal(semaphore);
> }];
>
> dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
dispatch_semaphore_wait() will block until the semaphore is signaled at the end
of the block.
Jeff Kelley
[email protected] | @SlaunchaMan | jeffkelley.org
On Jun 3, 2014, at 12:17 PM, Dave <[email protected]> wrote:
> I’ve tried that, addOperations:waitUntilFinished: waits for operations
> currently queued to finish before adding the current operation, it doesn’t
> Add it to the queue and then wait for it to complete which is what I want.
>
> Thanks
> Dave
>
> On 3 Jun 2014, at 19:26, Jeffrey Robert Kelley <[email protected]> wrote:
>
>> I think you’re looking for NSOperationQueue’s
>> -addOperations:waitUntilFinished: method. Should do what you want.
>>
>>
>> Jeff Kelley
>>
>> [email protected] | @SlaunchaMan | jeffkelley.org
>>
>> On Jun 3, 2014, at 5:51 AM, Dave <[email protected]> wrote:
>>
>>> Hi,
>>>
>>> I think this has been covered before, but all the searches I’ve done don’t
>>> really cover what I’d like to do.
>>>
>>> I have an API that has two modes of operation, Sync and Async.
>>>
>>> In Sync mode calls to the API MUST be on a background thread and the data
>>> is returned to the caller with a possibility that the thread is blocked
>>> until the operation has completed.
>>>
>>> In Async mode calls to the API may be on the background thread or the Main
>>> Thread, a delegate is passed to the API method which returns immediately
>>> and the Delegate is called when the operation completes or fails.
>>>
>>> This all works, however I have some existing code that I’d like to have the
>>> same API and be called by a “Manager Class” which calls the correct
>>> underlying API depending on the context, e.g.
>>>
>>> AppLayer—>ManagerClass—>API_A
>>> —>API_B
>>>
>>> API_A is the existing API supporting the Sync/Async interface.
>>> API_B is the one I wish to create.
>>>
>>> The problem is that the existing code uses NSOperationQueue/NSOperation
>>> accomplish it’s task, this works fine in Async mode, it was easy enough to
>>> adapt to call the Delegate methods, but I’m not sure how to implement Sync
>>> mode?
>>>
>>> Basically I want to add the NSOperation to the queue and then wait for it
>>> to complete before returning with the results.
>>>
>>> Any ideas suggestions would be greatly appreciated as there seem to be a
>>> lot of conflicting advice out there on how to do this and I’ve not been
>>> able to find anything worked as described above.
>>>
>>> Thanks a lot.
>>>
>>> All the Best
>>> Dave
>>>
>>>
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>>
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