iOS equivalent of setTimeout cancellation

    float interval = 0.5;
    
    if(!self.timer) {
        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
        dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
        dispatch_resume(timer);
        self.timer = timer;
    }
    
    dispatch_source_t timer = self.timer;
    dispatch_source_set_timer(timer, dispatch_walltime(DISPATCH_TIME_NOW, NSEC_PER_SEC * interval), interval * NSEC_PER_SEC, 0);
    dispatch_source_set_event_handler(timer, ^{
        dispatch_source_cancel(self.timer);
        self.timer = nil;
        [self loadVenuesForTable:self.searchDisplayController.searchResultsTableView withSearch:searchString];
    });

    
    return false;