> On 22 Jul 2014, at 8:42 am, Jens Alfke <[email protected]> wrote:
>
> I’m starting to port a pretty complex source base from using NSURLConnection
> to using NSURLSession. (Primarily because this is the only way to get around
> the only-four-sockets-per-host limitation.) I thought it was going to be
> straightforward, until I saw that NSURLSession only supports scheduling
> delegate calls on an NSOperationQueue, not an NSRunLoop. So that means I now
> also have to convert a number of runloop dependencies in the same code, which
> I don’t understand how to do.
>
> Case in point: I have a couple of things that require the use of delayed
> performs to schedule timing. What’s the equivalent of
> -performSelector:withObject:afterDelay: (or of NSTimer) for code that’s
> running under the control of an NSOperationQueue? I know this call won’t work
> on a queue (because the thread it’s on probably won’t have a runloop), but
> I’ve looked at the API docs and headers and don’t see anything comparable.
> Dispatch queues have dispatch_after, and I’d much rather use GCD than
> NSOperationQueue anyway*, but NSURLSession is forcing my hand.
>
> —Jens
>
> * (I know there’s now an underlyingQueue property on NSOperationQueue, but
> that’s only in iOS 8 and I can’t rely on that yet.)
You’d think that would be easy but it doesn’t seem that way. To make sure I
understand, you have callbacks on your NSOperationQueue from which you want to
then delay an operation on that same queue using NSTimer? I would probably
dispatch_after() back to the main queue, or a high- or low- priority, a block
which then re-enqueued the operation you wanted to perform back on the same
operations queue you started with.
ie if you have the operation you want to delay then mail-written code would
look something like
NSOperationQueue *myQueue = [ NSOperationQueue currentQueue ]; // if
you don’t already know what op queue you’re on
dispatch_after( dispatch_time( DISPATCH_TIME_NOW, delay * NSEC_PER_SEC ) ),
dispatch_get_<some>_queue() ){
[ myQueue addOperation:myOperation ];
};
I think that ought to work.
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