GCD定时器

by 伍雪颖

+ (GCDTimer *)repeatingTimer:(NSTimeInterval)seconds                                      block:(void (^)(void))block {  NSParameterAssert(seconds);  NSParameterAssert(block);  GCDTimer *timer = [[self alloc] init];  timer.block = block;  timer.source = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,                                        0, 0,                                        dispatch_get_main_queue());  uint64_t nsec = (uint64_t)(seconds * NSEC_PER_SEC);  dispatch_source_set_timer(timer.source,                            dispatch_time(DISPATCH_TIME_NOW, nsec),                            nsec, 0);  dispatch_source_set_event_handler(timer.source, block);  dispatch_resume(timer.source);  return timer;}- (void)invalidate {  if (self.source) {    dispatch_source_cancel(self.source);    self.source = nil;  }  self.block = nil;}

__block int n=0;    self.timer = [GCDTimer repeatingTimer:1 block:^{        n++;        NSLog(@"Hello");        if (n == 3) {            [self.timer invalidate];        }    }];

使用简单方便.