Re: How to get the dispatch queue for the current thread's runloop?
Re: How to get the dispatch queue for the current thread's runloop?
- Subject: Re: How to get the dispatch queue for the current thread's runloop?
- From: Ken Thomases <email@hidden>
- Date: Fri, 27 Jan 2012 20:41:13 -0600
On Jan 27, 2012, at 2:14 PM, Jens Alfke wrote:
> I'm really used to using -performSelector:withObject:afterDelay: to make something happen later. But I'd much rather use a block than a target/action. I can't find any API for this, however. Am I missing something? What I want is basically like
> PerformBlockAfterDelay(^{ …code here…}, 5.0);
>
> It looks like I should just call dispatch_async, but I'm unsure which dispatch queue to use. dispatch_get_main_queue only works for the main thread. Can I use dispatch_get_current_queue? I'm unsure of what this does when called on a background thread. The API docs say "If the call is made from any other thread, this function returns the default concurrent queue" … is that a queue associated with the thread's runloop, that's guaranteed to execute tasks on that thread?
There's no such thing as a dispatch queue for the current thread's run loop. The main thread's run loop also runs the main queue, as you've noted, but no other thread's run loop also runs a dispatch queue. In fact, in general, no other queue runs on any of your threads. libdispatch manages its own worker threads.
On Jan 27, 2012, at 4:19 PM, Marco Tabini wrote:
> I just use a little category on NSObject that I think I pulled from somewhere—but I can't remember where from:
> - (void) performBlock:(void (^)(void)) block afterDelay:(NSTimeInterval) delay {
> block = [block copy];
>
> [self performSelector:@selector(fireBlockAfterDelay:)
> withObject:block
> afterDelay:delay];
> }
>
> - (void)fireBlockAfterDelay:(void (^)(void))block {
> block();
> }
Believe it or not, this also works:
[(id)^{ ... code here ... } performSelector:@selector(invoke) withObject:nil afterDelay:5.0];
That is, you can target performSelector:withObject:afterDelay: at a block, itself, rather than some other helper object. And, a block implements the -invoke selector to, well, invoke itself.
Cheers,
Ken
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