OC 添加GCD 定时器

@property (nonatomic,strong) dispatch_source_t timer;

///不是在dealloc 修改为空
- (void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    if (self.timer){
        dispatch_source_cancel(self.timer);
        self.timer = nil;
    }
}


///使用
[self startCountDownAction];

///开启倒计时
- (void)startCountDownAction{
    NSLog(@"[self getDiffTime] = %@", [self getDiffTime]);
    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);
    self.timer = _timer;
    dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1*NSEC_PER_SEC, 0); //每秒执行
    @WeakObj(self);
    dispatch_source_set_event_handler(_timer, ^{
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"[self getDiffTime] = %@", [self getDiffTime]);
            @StrongObj(self);
            self.countDownLabel.attributedText = [self getDiffTime];
        });
    });
    dispatch_resume(_timer);
}



///9时22分32秒 8毫秒

///时间差
- (NSMutableAttributedString *)getDiffTime{
    
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDate *nowDate = [NSDate date];
    NSDateComponents *components = [calendar components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay fromDate:nowDate];
    ///今天0点
    NSDate *startDate = [calendar dateFromComponents:components];
    ///下一天的0点
    NSDate *endDate = [calendar dateByAddingUnit:NSCalendarUnitDay value:1 toDate:startDate options:0];
    
///俩日期差值
    double diffTime = [nowDate secondsEarlierThan:endDate];
    NSDate *detailDate = [NSDate dateWithTimeIntervalSince1970:diffTime];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; //实例化一个NSDateFormatter对象
    [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:8]];
    
    NSMutableAttributedString *dikou = [ToolUtil markString:@"距今日活动结束仅剩" color:colorFromRGB(0x434446) font:[UIFont regularFontOfSize:11]];
    [dateFormatter setDateFormat:@" H "];
    NSString *diffHour = [dateFormatter stringFromDate: detailDate];
    [dikou appendAttributedString:[ToolUtil markString:diffHour  color:colorFromRGB(0x1F1F20) font:[UIFont boldSystemFontOfSize:12]]];
    [dikou appendAttributedString:[ToolUtil markString:@"时"  color:colorFromRGB(0x434446) font:[UIFont boldSystemFontOfSize:11]]];
    
    [dateFormatter setDateFormat:@" m "];
    NSString *diffMinute = [dateFormatter stringFromDate: detailDate];
    [dikou appendAttributedString:[ToolUtil markString:diffMinute  color:colorFromRGB(0x1F1F20) font:[UIFont boldSystemFontOfSize:12]]];
    [dikou appendAttributedString:[ToolUtil markString:@"分"  color:colorFromRGB(0x434446) font:[UIFont boldSystemFontOfSize:11]]];
    
    [dateFormatter setDateFormat:@" s "];
    NSString *diffSecond = [dateFormatter stringFromDate: detailDate];
    [dikou appendAttributedString:[ToolUtil markString:diffSecond  color:colorFromRGB(0x1F1F20) font:[UIFont boldSystemFontOfSize:12]]];
    [dikou appendAttributedString:[ToolUtil markString:@"秒"  color:colorFromRGB(0x434446) font:[UIFont boldSystemFontOfSize:11]]];
    return dikou;
}




#pragma mark- ============ 富文本 ==============
+ (NSMutableAttributedString *)markString:(NSString *)str color:(UIColor *)color font:(UIFont *)font
{
    NSMutableAttributedString *attributedString_M = [[NSMutableAttributedString alloc] initWithString:str ];
    
    if ([self isNull:str]) {
        return attributedString_M;
    }
    if (![self isNull:color]) {
        [attributedString_M addAttribute:NSForegroundColorAttributeName
                                   value:color
                                   range:NSMakeRange(0, str.length)];
    }
    if (![self isNull:font]) {
        [attributedString_M addAttribute:NSFontAttributeName
                                   value:font
                                   range:NSMakeRange(0, str.length)];
    }
    
    return attributedString_M;
}





#pragma mark- 万能判空
+ (BOOL)isNull:(id)obj
{
    if ([obj isKindOfClass:[NSString class]]) {
        return obj == nil || [obj isEqual:[NSNull null]] || [obj isEqualToString:@"<null>"] || [self isEmpty:obj] || [obj isEqualToString:@"null"] || [obj isEqualToString:@"(null)"];
    } else {
        return obj == nil || [obj isEqual:[NSNull null]];
    }
}