根据日期计算发布时间段（NSCalendar）

// 返回发布时间dateWithString
- (NSString *)backReleaseTimeWithDateStr:(NSString *)dateWithString{
    // 获取当前NSCalendar
    NSCalendar *calendar = [NSCalendar currentCalendar];
    // 设置日期格式
    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
    //入参 发布日期
    NSDate *releaseTimer = [formatter dateFromString:dateWithString];
    if ([calendar isDateInToday:releaseTimer]) { // 今天
        //当前时间
        NSDate *nowDate = [NSDate date];
        // 获得日期之间的间隔
        NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;
        NSDateComponents *components = [calendar components:unit fromDate:releaseTimer toDate:nowDate options:0];
        if (components.hour >= 1) {
            //            formatter.dateFormat = @"今天 HH:mm";
            //            return [formatter stringFromDate:releaseTimer];
            return [NSString stringWithFormat:@"%zd小时前",components.hour];
        }else if(components.minute >= 1){
            return [NSString stringWithFormat:@"%zd分钟前",components.minute];
        }else{
            return @"刚刚";
        }
    }else if([calendar isDateInYesterday:releaseTimer]){  // 昨天
        formatter.dateFormat = @"昨天 HH:mm";
        return [formatter stringFromDate:releaseTimer];
    }else {  // 其他
        formatter.dateFormat = @"MM-dd HH:mm";
        return [formatter stringFromDate:releaseTimer];
    }
    return dateWithString;
}