NSTimer callback on background thread

Question

I have a NSTimer defined as follows:

timer = [NSTimer scheduledTimerWithTimeInterval:30
                                         target:self
                


        

Answer 1

If you want to run a timer on a background thread, the most efficient way to do that is with a dispatch timer:

@property (nonatomic, strong) dispatch_source_t timer;

and you can then configure this timer to fire every two seconds:

- (void)startTimer {
    dispatch_queue_t queue = dispatch_queue_create("com.domain.app.timer", 0);
    self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    dispatch_source_set_timer(self.timer, dispatch_walltime(NULL, 0), 2.0 * NSEC_PER_SEC, 0.1 * NSEC_PER_SEC);
    dispatch_source_set_event_handler(self.timer, ^{
        // call whatever you want here
    });
    dispatch_resume(self.timer);
}

- (void)stopTimer {
    dispatch_cancel(self.timer);
    self.timer = nil;
}