gistfile1.m

        
        @property (nonatomic, strong) dispatch_source_t serverPollTimer;
        
        /* ___ */
        __weak typeof(self) weakSelf = self;
        self.serverPollTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());
        dispatch_source_set_timer(self.serverPollTimer, dispatch_walltime(NULL, 7*NSEC_PER_SEC), 7*NSEC_PER_SEC, 1e8);
        dispatch_source_set_event_handler(self.serverPollTimer, ^{
            [weakSelf updateCurrentJobState];
        });
        dispatch_resume(self.serverPollTimer);