全局方法

/**
 倒计时

 @param time 时间
 @param countDownBlock 倒计时阶段执行
 @param endBlock 结束后执行
 */
+ (void)countDownWithTime:(int)time
           countDownBlock:(void (^)(int timeLeft))countDownBlock
                 endBlock:(void (^)())endBlock
{
    __block int timeout = time; //倒计时时间
    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_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行
    dispatch_source_set_event_handler(_timer, ^{
        if(timeout<=0){ //倒计时结束，关闭
            dispatch_source_cancel(_timer);
            dispatch_async(dispatch_get_main_queue(), ^{
                if (endBlock) {
                    endBlock();
                }
            });
        } else {
            dispatch_async(dispatch_get_main_queue(), ^{
                if (countDownBlock) {
                    [UIView beginAnimations:nil context:nil];
                    [UIView setAnimationDuration:1];
                    countDownBlock(timeout);
                    [UIView commitAnimations];
                }
                timeout--;
            });
        }
    });
    dispatch_resume(_timer);
}

调用方法：

  [GlobalFunc countDownWithTime:5 countDownBlock:^(int timeLeft) {
               [self.button setTitle:[NSString stringWithFormat:@"%d 跳过",timeLeft] forState:UIControlStateNormal];
    } endBlock:^{
        [UIView animateWithDuration:0.4 animations:^{
            self.alpha = 0.0f;
        } completion:^(BOOL finished) {
            [self removeFromSuperview];
            
        }];
    }];