CODEWITHSUNDEEP
iosgrand-central-dispatch
Patrick
Patrick

Reputation: 83

In GCD, is there a way to tell if the current queue is concurrent or not?

In GCD, is there a way to tell if the current queue is concurrent or not? I'm current attempting to perform a delayed save on some managed object contexts but I need to make sure that the queue the code is currently executed on is thread-safe (in a synchronous queue).

Upvotes: 3

Views: 1185

Answers (2)

jkh
jkh

Reputation: 3266

If you actually have to determine whether or not the queue passed in to you is serial or concurrent, you've almost certainly designed things incorrectly. Typically, an API will hide an internal queue as an implementation detail (in your case, your shared object contexts) and then enqueue operations against its internal queue in order to achieve thread safety. When your API takes a block and a queue as parameters, however, then the assumption is that the passed-in block can be safely scheduled (async) against the passed-queue (when, say, an operation is complete) and the rest of the code is factored appropriately.

Upvotes: 4

Stephen Searles
Stephen Searles

Reputation: 981

Yes, assuming you're doing the work in an NSOperation subclass:

[myOperation isConcurrent] //or self, if you're actually in the NSOperation

If you need to ensure some operations are always executed synchronously, you can create a specific operation queue and set its maximum concurrent operations to 1.

NSOperationQueue * synchronousQueue = [[NSOperationQueue alloc] init];
[synchronousQueue setMaxConcurrentOperationCount:1];

GCD takes some planning ahead. The only other way I can think of is to observe the value isExecuting (or similar) on your NSOperation objects. Check out this reference on that. This solution would be more involved, so I hope the other one works for you.

Upvotes: -1

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