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Re: Question about dispatch_timer function
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Re: Question about dispatch_timer function


  • Subject: Re: Question about dispatch_timer function
  • From: Dave Zarzycki <email@hidden>
  • Date: Thu, 26 Apr 2012 16:19:00 -0700

On Apr 25, 2012, at 6:07 PM, Kévin Vavelin <email@hidden> wrote:

> Hi there,
>
> I've a question about the dispatch_timer function. I try to make a strobe flash on my iPhone app and for that i used an NSTimer but a friend of mine say that it's better to use dispatch function. So i was looking and try to implement something. I explain my code before post anything :
> I have a UISlider in another view (settings.strobeValue) and get his value for settings the timer. And i called changeStrobeState in another function who wll be called by dispatch function. But when i hit the button on my view and send my dispatch code, no work at all... So there is the code :
>
> -(void)changeStrobeState
> {
>    if (NO == [[NSUserDefaults standardUserDefaults] boolForKey:@"buttonStrobeState"])
>    {
>        [deviceCapture lockForConfiguration:nil];
>        [deviceCapture setTorchMode:AVCaptureTorchModeOff];
>        [deviceCapture unlockForConfiguration];
>    }
>    else
>    {
>        [deviceCapture lockForConfiguration:nil];
>        [deviceCapture setTorchMode:AVCaptureTorchModeOn];
>        [deviceCapture unlockForConfiguration];
>    }
>    BOOL state = [[NSUserDefaults standardUserDefaults] boolForKey:@"buttonStrobeState"];
>    [[NSUserDefaults standardUserDefaults] setBool:!state forKey:@"buttonStrobeState"];
>
> }
>
>
> - (dispatch_source_t)setupStrobeTimer {
>    static dispatch_once_t onceToken;
>    dispatch_once(&onceToken, ^{
>        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
>         _strobeTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
>        if (_strobeTimer) {
>            dispatch_source_set_timer(_strobeTimer, dispatch_walltime(DISPATCH_TIME_NOW, settings.strobeValue * NSEC_PER_SEC),
>                                      settings.strobeValue * NSEC_PER_SEC, 6ull * NSEC_PER_SEC);
>            __block ViewController *blockSelf = self;
>            dispatch_source_set_event_handler(_strobeTimer, ^{
>                [blockSelf changeStrobeState];
>            });

Kévin,

Your code is not calling dispatch_resume() on the timer source. Please review the man page and/or other documentation.

davez

>        }
>    });
>    return _strobeTimer;
> }
>
> Can you help me ?
>
> Thanks for reading and sorry 'cause my english is not perfect and it's actually 3 AM here :)
>
> Cheers,
> Vavelin Kevin
> Twitter | Blog | Viadeo
>
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References: 
 >Question about dispatch_timer function (From: Kévin Vavelin <email@hidden>)

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