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    <p>You probably don't want to check something as fast as possible, since that would lead to performance issues.</p> <p>If you want something that updates with the display, you could use <a href="http://developer.apple.com/library/ios/#documentation/QuartzCore/Reference/CADisplayLink_ClassRef/Reference/Reference.html" rel="nofollow">CADisplayLink</a>. You can google around for examples, like this <a href="http://zearfoss.wordpress.com/2011/03/09/drawing-with-cadisplaylink/" rel="nofollow">one</a>.</p> <p>If you don't need to link it to display refresh, you can set up an <a href="https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSTimer_Class/Reference/NSTimer.html" rel="nofollow">NSTimer</a>, or use a variant of <a href="http://developer.apple.com/library/Mac/#documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/Reference/Reference.html#//apple_ref/occ/instm/NSObject/performSelector%3awithObject%3aafterDelay%3ainModes%3a" rel="nofollow">performSelector:withObject:afterDelay</a>.</p> <p>If you need high resolution timers, look at <a href="http://developer.apple.com/library/ios/#technotes/tn2169/_index.html" rel="nofollow">this technical note</a>.</p> <p>NSTimer and performSelector both have a resolution around 50-100 ms, which is not sufficient for sound playback.</p> <p>I would recommend you use a separate real time thread with mach_wait_until() as explained in the tech note. Using the code from <strong>Listing 2</strong> in the technote, something playing a sound every <code>BEATS_PER_SEC</code> using <code>play_beat()</code>, would look like this:</p> <pre><code>void play_beat_thread(int argc, const char * argv[]) { mach_timebase_info(&amp;timebase_info); uint64_t time_to_wait = nanos_to_abs(10ULL * BEATS_PER_SEC); uint64_t next = mach_absolute_time(); while (true) { next = next + time_to_wait; mach_wait_until(next); play_beat(); } } </code></pre> <p>If you want more advice on high resolution audio timing, I suggest you reframe this question along the lines <em>"How do I manually schedule high resolution audio playback on iOS/OS X"</em>.</p>
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    1. POCocos2d update function equivalent?
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    1. COHmm. The app I'm working on is a beat sequencer so I'm trying to check for beats to play based on elapsed time. I might be able to essentially have the check recursively call itself every x amount of time so I literally only am checking every time I need to check. That would be very efficient!
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      1. USLogan Shire
    2. CO@LoganShire if 60 checks / s is enough, CADisplayLink might be sufficient. NSTimer usually doesn't provide high resolution timing. You should also consider what thread you're using to do this. You can't do a busy-loop on the main thread without locking the entire UI. I added a link to a technical note regarding high resolution timers. It has some examples that should get you started if you need to check very often. Be wary of threading issues though.
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    3. COI'm gonna try the recursive perform selector solution and see if that works as it would be by far the most efficient solution, as it only would call every time I need to update. If that doesn't work I'll try the display link.
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      1. USLogan Shire
 

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