Question

我有一个工作日的面具编号，代表一周中几天的总和：

SUNDAY = ((2**0))
MONDAY = ((2**1))
TUESDAY = ((2**2))
weekdays_mask = SUNDAY + MONDAY + TUESDAY

因此，如果我将这些天的总和存储在数据库中，我该如何执行相反的过程并找到我必须根据weekdays_mask值显示的星期几。有谁知道这样做的方法？谢谢！

Answer 1

+有点不常见。您通常使用按位OR 来组合值：

SUNDAY | MONDAY | TUESDAY #=> 7
SUNDAY | MONDAY           #=> 3

和按位AND 检查特定值：

days = SUNDAY | MONDAY

days & SUNDAY  #=> 1
days & MONDAY  #=> 2
days & TUESDAY #=> 0   <- zero indicates bit not set

Answer 2

您可以通过类似0b0000的模式初始化它们，而不是+/-然后使用二进制算术代替;

SUNDAY    = 0b000000
MONDAY    = 0b000001
TUESDAY   = 0b000010
WEDNESDAY = 0b000100
THURSDAY  = 0b001000
FRIDAY    = 0b010000
SATURDAY  = 0b100000

weekend = SATURDAY | SUNDAY
workday = MONDAY | TUESDAY | WEDNESDAY | THURSDAY | FRIDAY

is_friday_weekend = weekend & FRIDAY
# => 0

is_friday_workday = workday & FRIDAY
# => 16 (Which is not 0; so yes)

Answer 3

我确定有一种更干净的方式，在这里我的2美分，基于三天，但也可以增加更多的日子：

SUNDAY = ((2**0))
MONDAY = ((2**1))
TUESDAY = ((2**2))
weekdays_mask_7 = SUNDAY | MONDAY | TUESDAY
weekdays_mask_6 = MONDAY | TUESDAY
weekdays_mask_5 = SUNDAY | TUESDAY
weekdays_mask_4 = TUESDAY
weekdays_mask_3 = SUNDAY | MONDAY
weekdays_mask_2 = MONDAY
weekdays_mask_1 = SUNDAY

days = %w[SUNDAY MONDAY TUESDAY]

weekdays_mask = weekdays_mask_7 # just to play

day_array = (weekdays_mask.to_s(2).split("").map(&:to_i).reverse).zip(days)
day_array.select{|e| p e[1] if e[0] == 1}

根据工作日的掩码值查找星期几

3 个答案: