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#pragma mark 更新时间字符串
- (void)updateTimeLabel
{
    if (!self.lastUpdateTime) return;
    
    // 1.获得年月日
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSUInteger unitFlags = NSYearCalendarUnit| NSMonthCalendarUnit | NSDayCalendarUnit |NSHourCalendarUnit |NSMinuteCalendarUnit;
    NSDateComponents *cmp1 = [calendar components:unitFlags fromDate:_lastUpdateTime];
    NSDateComponents *cmp2 = [calendar components:unitFlags fromDate:[NSDate date]];
    
    // 2.格式化日期
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    if ([cmp1 day] == [cmp2 day]) { // 今天
        formatter.dateFormat = @"今天 HH:mm";
    } else if ([cmp1 year] == [cmp2 year]) { // 今年
        formatter.dateFormat = @"MM-dd HH:mm";
    } else {
        formatter.dateFormat = @"yyyy-MM-dd HH:mm";
    }
    NSString *time = [formatter stringFromDate:self.lastUpdateTime];
    
    // 3.显示日期
    self.lastUpdateTimeLabel.text = [NSString stringWithFormat:@"最后更新：%@", time];
}